Fix the life cicle of the FcCharSet objects.

Fix the life cicle of the FcCharSet objects.

* Pointer to this objects were kept in the caches
  without taking care too much of the FcPattern objects
  that hold them.
  The fon client increases now the reference counter of
  these objects when they are stored in the caches.

* The new mFontIdCache, mPixelBufferCache, mEmbeddedItemCache
  and mBitmapFontCache caches were not cleared in the
  ClearCache() method.

[Model] Gear Watch Designer
[BinType]
[Customer]
[Issue#]
[Request]
[Occurrence Version]
[Problem]
[Cause & Measure] As described above.
[Checking Method]
[Team] SRUK
[Developer] Victor Cebollada
[Solution company] Samsung
[Change Type]

Change-Id: Ieb8590a786111f88676c305c9e1a17232288a61e
Signed-off-by: Victor Cebollada <v.cebollada@samsung.com>