CCLabel 采用 TTFLabel来显示,为了更好的支持ttf字体
为了配合Cocostudio的默认字体,添加了默认字体参数.
update
Merge branch 'master' of
https://github.com/121077313/cocostudio-ui-libgdx.git

Conflicts:
	cocostudio-ui-libgdx/src/cocostudio/ui/CocoStudioUIEditor.java
	cocostudio-ui-libgdx/src/cocostudio/ui/parser/group/CCPanel.java
	cocostudio-ui-libgdx/src/cocostudio/ui/parser/widget/CCLabel.java