Don't require a colon for cmap commands to hl cmds

Because we are already in command-line mode.

Thanks to filterfalse.
Break up lines that exceed limit of 80 characters
Fix highlighting of :command!

Didn't highlight because of trailing exclamation mark.

Thanks to filterfalse.
Don't highlight arguments of :source in any way

I didn't like that it highlighed .vifm extension of files.
Merge branch 'more-syntax-hl-improvements'