Working with text styles
Merge branch 'master' of https://github.com/e-ucm/ead into styled-text
Merge branch 'master' of https://github.com/e-ucm/ead into styled-text

Conflicts:
	engine/core/src/main/java/es/eucm/ead/engine/renderers/TextEngineObject.java
Merge branch 'master' of https://github.com/e-ucm/ead into styled-text
Basic implementation of text styles. Roughly speaking, all text attributes related to how it is rendered (scale, font, color) have been encapsulated into the TextStyle wrapper.

The style of a Text object can be defined directly into the object or through a reference to a file. This allows rapidly changing the appearance of all the text in a game, in one shot, but also personalizing the attributes for a particular piece of text.

Text style is optional. If not set, a basic white, 1.0F style is used.
Added new galleries system. The galleries extends BaseGallery.java
Added filter tags panel
Merge branch 'master' of https://github.com/e-ucm/ead into styled-text
Reviewing serializers and loaders (not only texts but all of them). Many serializers and loaders have been deleted and replaced by generic ones that avoid repeating code.

SceneElementSerializer has not been edited. We should decide on what to do with this in the near future (I'll open a different issue)
Updated editor android project.properties to API 15
Game view now draws scene limits
Added scenes list
Fixes in columnslayout
Format
Prevent transparent color in batch
Draw game view port using view scale
Refactored leftright topbottom layout with sides layout
Changes to the skin
Added toggle images widget
Added toggle images controller