Fix type in docs describing cropping specifier

Thanks to Stas Malavin.
Improved documentation on :file[x]type commands

Thanks to Stas Malavin.
Improved documentation time sorting keys

Thanks to Stas Malavin.
Merge branch 'improve-filextype-docs'

Improve documentation on :file[x]type commands and time sorting keys.
Also fixed a typo.

Thanks to Stas Malavin.