Added YouTubeSearch to YouTube module.

+ plugins/youtube/search.py (YouTubeSearch)
    - Active command, triggers on '!yt'
    - Examples:
        !yt query
        !yt "multiword query"
        a line with a !yt query inside
        a line with a !yt "longer query" inside

    - Added a test for searching by simple keyword.

+ Renamed youtube.py back to ident.py :U

+ plugins/youtube/youtube_settings_template.ini
    - Fill in your YouTube API key here for search. Required for now.