Add raw files support to Langchecker

## Classes
New methods in Project:
* getWebsitesByDataType: retrieve only websites with a specific data type
* getWebsiteDataType: retrieve a website's data type

New class RawManager:
* compareRawFiles: used to compare 2 raw files, return array of results based on hash and date comparisons

Added tests for new methods and class.

## Views
Errors:
* Display an error in locales for missing files only if the don't have the 'optional' flag.
* Display an error for missing reference files.

Export:
* Add 'status' attribute to JSON for raw files instead of identical, missing, etc.. Possible values: untranslated, outdated, ok, missing_reference, missing_locale.
* Add 'data_source' attribute for all files (possible values: 'lang', 'raw').

Globalstatus:
* Display a different table for raw files, with only a status link.

Listpages:
* Display only status link for raw files.

Listsitesforlocale:
* Add table to display raw files status.

All other views remain available only for .lang files.