IDE-1229

  Add some features for liferay language file

  - Create a content type of which encoding is UTF-8 for liferay language
    file.
  - Add an action in the project popup menu to encode language file to UTF-8
  - Add a project validator to validate the language properties, show warning
    message and fix that by active Qucik Fix in the right-click menu of the
    problem.
IDE-1229

Source review and optimize the use of resource proxy.
IDE-1229

Source review.