[subset] Add --glyphs
[subset] Accept separate on whitespace as well as comma

For all options, including the newly added --glyphs.
[subset] Minor
[subset] allow for unicode-based name with suffixes in the subset list

Fixes https://github.com/behdad/fonttools/issues/133

That part of the code is becoming really messy, but I want to get
all the features in first, then clean up.