Add switch to hide messages of any given severity

[ThorArise]

As of now only switches to hide info and warning severity messages are present. Both locally and in CI builds it can be useful to filter findings based on the severity of all levels. To avoid adding two more switches, the two present switches have been removed in favor of a generic "hide" switch to disable specified severity level messages.

Pull request checklist

Bugfix

• [ ] A testcase was added to test the behavior

New feature

• [x] A testcase was added to test the behavior
• [x] wiki-creator.py was run and a new wiki document was filled with information
• [x] New functions are documented with docstrings
• [x] No debug code is left
• [x] README.md was updated to reflect the changes (check even if n.a.)

[priv-kweihmann]

@ThorArise I like the idea of the PR. But please enable a seamless transition for everyone by slowly phasing out the old parameters (nowarn and noinfo)

[ThorArise]

• Removed any reference to neutral severity
• re added nowarn and noinfo as legacy interface (no documentation)

[priv-kweihmann]

@ThorArise

README.md:72: speicified ==> specified
oelint_adv/__main__.py:50: speicified ==> specified

please fix those two typos here

[ThorArise]

typos are fixed