Somewhat standardize cvar descriptions

Somewhat standardize cvar descriptions

This commit isn't comprehensive, it mostly served to put all descriptions in a consistent format so that a script (added in a future commit) can sed replace them without exceptions where it doesn't work properly because the cvar has a different format than expected.
Description formatting rules used here thusfar will be outlined in such future commit.
Other rules applied so far include:
- making words like Devastator, Jetpack, Keepaway, etc. capitalized
- added "// script-ignore" on cvars which shouldn't be touched by the script
- option-lists (like "\"0\" = disabled, \"1\" = enabled") should be preceded by "; "
- etc.
Fixed any spelling errors I noticed.
Fully updated notifications.cfg, which will be excluded by the script due to the comment at the top of the file.
Didn't yet Americanize spelling.
Included AUTOCVAR_* descriptions.