transifex OAuth support + Mobile templates + 2 new api requests

Hello guys,
 this patch adds OAuth support so that more developers will be able to build upon the transifex platform without risking the platform's security.

In detail:

1) I've added patches for django-piston: https://github.com/fazakis/django-piston(don't forget to apply these patches) and transifex CE so OAuth can work correctly

2) I've added mobile templates for signin and authorization (so that mTx can work)
(/mobile/accounts/signin/ and e.t.c. urls ) these templates can also be used as a nice base extension of mobile tf.

3) I've added 2 new api requests(search projects and get user dashboard projects) to the transifex api accessible from /mobile/api/2/

4) I've started building a Mobile Transifex Client which utilizes all the above functionality found here https://github.com/fazakis/mtx (note some functionality is not working correctly due to transifex CE old api bugs)

Hint: i tried to implement the above from within a new module called mobile so changes will have the lowest possible impact in transifex codebase itself.

TODO:
1) decide for access token expiration times
2) handle some way the recreation of access tokens for apps and users that've already issued a valid access token (multiple access tokens, bad thing)

I have not tested extensively the new functionality cause of lack of time but for sure oauth GET POST PUT DELETE requests do work as you can Test using the mTx project.

For any questions reach me at: gccster@gmail.com

Thanks and Cya