Initial Stylesheet parser implementation

[nelson-glauber]

This PR includes the following changes:

• Initial implementation of stylesheet parser. It is implemented as a separate module called stylesheet-parser and it uses Antlr library.
• In order to test this approach the following modifiers where implemented:
  • align #216 and #223
  • alignByBaseline #219
  • aspectRatio #316
  • border #227 and #229
  • background #232
  • clip #234
  • padding #268 , #269 , #270, and #271
  • fillMaxHeight #326
  • fillMaxWidth #328
  • height #329 #320
  • size #339 #341
  • width #343 #323