Implement XEP-0272: Multiparty Jingle (Muji) stanza parts

[melvo]

PR check list:

• [x] Document your code
• [x] Add \since QXmpp 1.X, QXMPP_EXPORT
• [x] Fix doxygen warnings (see log when building with -DBUILD_DOCUMENTATION=ON)
• [x] Update doc/doap.xml
• [x] Add unit tests
• [x] Format the code: Run clang-format -i src/<edited-file(s)> tests/<edited-file(s)>

[codecov[bot]]

Codecov Report

Base: 68.63% // Head: 68.48% // Decreases project coverage by -0.15% :warning:

Coverage data is based on head (4aa1a28) compared to base (50be942). Patch coverage: 96.15% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #457 +/- ## ========================================== - Coverage 68.63% 68.48% -0.16% ========================================== Files 275 279 +4 Lines 23905 24359 +454 ========================================== + Hits 16407 16682 +275 - Misses 7498 7677 +179 ``` | [Impacted Files](https://codecov.io/gh/qxmpp-project/qxmpp/pull/457?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qxmpp-project) | Coverage Δ | | |---|---|---| | [src/base/QXmppJingleIq.h](https://codecov.io/gh/qxmpp-project/qxmpp/pull/457/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qxmpp-project#diff-c3JjL2Jhc2UvUVhtcHBKaW5nbGVJcS5o) | `100.00% <ø> (ø)` | | | [src/base/QXmppPresence.h](https://codecov.io/gh/qxmpp-project/qxmpp/pull/457/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qxmpp-project#diff-c3JjL2Jhc2UvUVhtcHBQcmVzZW5jZS5o) | `100.00% <ø> (ø)` | | | [tests/qxmppjingleiq/tst\_qxmppjingleiq.cpp](https://codecov.io/gh/qxmpp-project/qxmpp/pull/457/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qxmpp-project#diff-dGVzdHMvcXhtcHBqaW5nbGVpcS90c3RfcXhtcHBqaW5nbGVpcS5jcHA=) | `100.00% <ø> (ø)` | | | [src/base/QXmppJingleIq.cpp](https://codecov.io/gh/qxmpp-project/qxmpp/pull/457/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qxmpp-project#diff-c3JjL2Jhc2UvUVhtcHBKaW5nbGVJcS5jcHA=) | `86.09% <83.33%> (-0.01%)` | :arrow_down: | | [src/base/QXmppPresence.cpp](https://codecov.io/gh/qxmpp-project/qxmpp/pull/457/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qxmpp-project#diff-c3JjL2Jhc2UvUVhtcHBQcmVzZW5jZS5jcHA=) | `93.99% <100.00%> (+0.72%)` | :arrow_up: | | [tests/qxmpppresence/tst\_qxmpppresence.cpp](https://codecov.io/gh/qxmpp-project/qxmpp/pull/457/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qxmpp-project#diff-dGVzdHMvcXhtcHBwcmVzZW5jZS90c3RfcXhtcHBwcmVzZW5jZS5jcHA=) | `99.15% <100.00%> (+0.12%)` | :arrow_up: | | [src/base/QXmppError.h](https://codecov.io/gh/qxmpp-project/qxmpp/pull/457/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qxmpp-project#diff-c3JjL2Jhc2UvUVhtcHBFcnJvci5o) | `0.00% <0.00%> (ø)` | | | [src/base/QXmppError.cpp](https://codecov.io/gh/qxmpp-project/qxmpp/pull/457/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qxmpp-project#diff-c3JjL2Jhc2UvUVhtcHBFcnJvci5jcHA=) | `0.00% <0.00%> (ø)` | | | [src/base/QXmppBitsOfBinaryData.cpp](https://codecov.io/gh/qxmpp-project/qxmpp/pull/457/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qxmpp-project#diff-c3JjL2Jhc2UvUVhtcHBCaXRzT2ZCaW5hcnlEYXRhLmNwcA==) | `100.00% <0.00%> (ø)` | | | [tests/qxmpputils/tst\_qxmpputils.cpp](https://codecov.io/gh/qxmpp-project/qxmpp/pull/457/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qxmpp-project#diff-dGVzdHMvcXhtcHB1dGlscy90c3RfcXhtcHB1dGlscy5jcHA=) | `100.00% <0.00%> (ø)` | | | ... and [10 more](https://codecov.io/gh/qxmpp-project/qxmpp/pull/457/diff?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qxmpp-project) | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qxmpp-project). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qxmpp-project)

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