Added black outlines to 24x24, 32x32 and 48x48 icons to improve visibility
Replaced 16x16 icons whith monoblack icons, to make them visible in menus
Merge pull request #619 from opentx/dvogonen/add_monowhite_borders

Added black outlines to 24x24, 32x32 and 48x48 icons to improve visibili...