updated i18n integration

This is i18n integration taking into account all the previous requested changes.

The series of pull requests also includes:
https://github.com/punkave/apostrophe/pull/102
https://github.com/punkave/apostrophe-pages/pull/10
https://github.com/punkave/apostrophe-map/pull/3
https://github.com/punkave/apostrophe-people/pull/7
https://github.com/punkave/apostrophe-groups/pull/4
https://github.com/punkave/apostrophe-snippets/pull/18
https://github.com/punkave/apostrophe-blog/pull/6
https://github.com/punkave/apostrophe-events/pull/4
https://github.com/punkave/apostrophe-editor-2/pull/25
https://github.com/punkave/apostrophe-sandbox/pull/31
https://github.com/punkave/appy/pull/4

All the above are tested in a staging environment. The sandbox works out of the box, with only a small .gitignore added. (TODO: wrap stuff in sandbox with `__()`)
 
### Important changes to note
* The email mixin now requires `res` as well as `req` to be able to do `__()`
* In various places, res was added as well as req, since i18n puts its' __() local on the res object

### Untested modules
The following modules would need testing, I skimmed over them to see that nothing would clash. You don't have to use `__()` in your views after all:
* apostrophe-fancy-page
* apostrophe-moderator
* apostrophe-twitter
* apostrophe-rss
* apostrophe-blocks
* apostrophe-button

They should work without any change. They will require wrapping in __() to be i18n enabled.