FontClient - Fix font selection issues.

* Fix for scalable/color fonts.
  Before this patch it was assumed that a font with fixed
  glyph's sizes  was a color font. Wrong!
  A scalable non color font may have fixed sizes as well.
  As a result of this some glyphs were missing.

* Fix the issue when a font doesn't support all the glyphs
  of a script.
  i.e a font validated for the CJK script may contain
  glyphs for the chinese language but not for the
  Japanese.
  Some glyph's bitmaps failed to be retrieved showing
  squares instead of the actual glyph.

  The font's character set is cached and a new
  IsCharacterSupportedByFont() method has been added to
  query if a character is supported.

Change-Id: I804cfa83fafd0ae7c1e199af48c6f728740816c2
Signed-off-by: Victor Cebollada <v.cebollada@samsung.com>