[doc] Summarize class options into a single section/subsection

[louisstuart96]

Currently beamer class options are seperately distributed in the entire documentation, and some deprecated options are not listed. It's necessary to summarize them in a clear list, for example, in alphabetic order.

[dbitouze]

Another possibility: gather them in the index as subentries of an entry "Options".

[louisstuart96]

@dbitouze There is already an entry 'Class options for beamer', but that might not be enough.

[dbitouze]

There is already an entry 'Class options for beamer', but that might not be enough.

@louisstuart96 Indeed, I missed it :worried:

[titanic-jb]

Having asked the same question as #688, I strongly support the idea, to have a section of their own.