Add option to not generate "Since: [ver]" in docs

[JohannesSchilling]

We were not using the version-info in a project at work, so i added an option to not generate them in the first place. Keeping the default to the current behaviour, i thought maybe upstream could want this change as well.

[coveralls]

Pull Request Test Coverage Report for Build 103

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 42 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.05%) to 89.333%

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Files with Coverage Reduction	New Missed Lines	%
/home/travis/virtualenv/python3.5.6/lib/python3.5/site-packages/doxyqml-0.5.0-py3.5.egg/doxyqml/main.py	14	68.22%
/home/travis/virtualenv/python3.6.3/lib/python3.6/site-packages/doxyqml-0.5.0-py3.6.egg/doxyqml/main.py	14	68.22%
/home/travis/virtualenv/python3.4.6/lib/python3.4/site-packages/doxyqml-0.5.0-py3.4.egg/doxyqml/main.py	14	68.22%

Totals
Change from base Build 102:	0.05%
Covered Lines:	1072
Relevant Lines:	1200

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💛 - Coveralls

[agateau]

Looks good, thanks!

Can you add a functional test for this option? I just added support for testing command line arguments to Doxyqml functional test "framework". It's documented in https://github.com/agateau/doxyqml/blob/master/tests/functional/README.md.

You can start from the "namespace" test as an example.

[JohannesSchilling]

rebased onto latest master and added a functional test to test the absence of the "Since: .." version entry.

[agateau]

Sorry for the delay, looks great now, merging it. Thanks again!