Character map could be unsorted and glyphs sorted

The character regions in a spritefont file could be specified in any order. The FontDescription.Characters list would remain in this unsorted order. After glyphs were imported, the glyphs list was sorted based on Glyph.Character.  The SpriteFontContent had already copied the unsorted character list.

The fix is not copy the character list when creating the SpriteFontContent and populate it from the sorted glyph list when all other glyph information is added to the SpriteFontContent.

Fixes #2924