Strip() various name attributes

Continuation of https://github.com/googlefonts/fontmake/issues/349 and https://github.com/googlefonts/glyphsLib/issues/540.

Users sometimes make errors of the "space at the end of something" variety, e.g. in layer names, family/style names, etc. Compile a list of things to `.strip()` automatically and always do that? Would need check for e.g. the case where someone has a layer named "Support" and another called "Support ".