Deprecate functions *_join

[thpralas]

This PR deprecates following functions :

• full_join
• inner_join
• left_join
• right_join

These functions were aliases for mergeSEs with parameter join, thus they do not need to be replaced.

[antagomir]

Could you check that we have at least one example in OMA Ch. 3 about using the SEtools if these are removed from here?

[TuomasBorman]

We still have mergeSEs function. The intention was to remove these aliases; they make things more complicated without adding value

[antagomir]

right - and in fact we already have examples in oma as well so I guess it is Ok

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 24 lines in your changes are missing coverage. Please review.

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Files	Patch %	Lines
R/deprecate.R	0.00%	24 Missing :warning:

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```diff @@ Coverage Diff @@ ## devel #515 +/- ## ======================================== Coverage ? 72.20% ======================================== Files ? 40 Lines ? 4677 Branches ? 0 ======================================== Hits ? 3377 Misses ? 1300 Partials ? 0 ```

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