Merge features from dev to master

Features:

• Added more keywords to specify resolutions. E.g. you can use --quality low to download a recording in 360p. (part of #5 (closed))
• Print selected resolution for downloading at beginning of script (part of #5 (closed))
• Allow comments in parameter file

Breakage:

• Changed mapping for HD from 1080p to 720p and added a mapping for FullHD to 1080p (part of #5 (closed))