commentTools.macroSelection for adding macro text
"+add macro" button added to macros dropdown
just the regular one, not any category'd ones
refactor default macros into buildMacroDropdowns, use general-use function
automatically hide macro dropdown list when choosing macro (optional, default=hide)
Closes https://github.com/honestbleeps/Reddit-Enhancement-Suite/issues/507
move default macros back out of buildMacroDropdowns
move addMacroButton out of buildMacroDropdowns too
Merge pull request #508 from andytuba/issue_507

Add "+ macro" button back to macro dropdown