Apply correct color to Header Bar menu item text

Refs #206
Improved method of generating a new control class instance
Move compatibility-related functions to a new include file.

Also replace current_action() function with identical current_filter().
The former was introduced in WP 3.9, and was causing some people's sites
to fatal because they were using an older version.
Consolidate ttfmake_sanitize_text(), add additional tags, make it filterable

Refs #200
Update changelog for 1.4.3
Bump version to 1.4.3
Add setting arguments inline so Theme Check can verify sanitize_callback
Update .pot file again
Merge branch 'release-1.4.3' into develop
Version 1.4.3