Refactor syntastic deactivation

Add eclim#lang#isFiletypeValidationEnabled and
eclim#lang#disableSyntasticIfValidationIsEnabled and call the latter
from filetype files.

TODO: this commit contains the change for php.vim only, but should get
used for the other filetypes, when accepted.
changes to new syntastic deactivation logic

- minor changes to conform to exsting eclim coding style
- fix a bug on setting the syntastic checkers
- add new function call to remaining syntastic + eclim supported file
  types
- re-add ability to force both syntastic and eclim's validation to both
  be enabled

refs #281