Implemented several minor optimizations
- HardwareFont.as now stores frequently requested values like uniqueIdentifier, ascender, etc.
- HardwareCharacterCache.as can now clear it's instance cache.
- HardwareGlyphInstance.as now implements a basic pool to which hardware glyph instances can be returned and retrieved from.
- Fixed a bug in LinkedList.as which would cause errors if the very first or last element of a list would be removed. This bug did not occur with circular linked lists.