Main function and other improvements.

Added:
- The ability to upload extensions from a local computer.
- The ability to upload extensions from a remote server.
- Russian language.
- #1 functions.
- More descriptions.

Some useful fixes for existing functions.

Deleted:
- Unnecessary tree functions (we can add a new extension for it) as there's no need in it now - users simply click `Upload`, then `Enable` without any other steps.
- We're back to the globals as they're used all over module pages. $this is currently used in any other pages.

Screenshot:
![upload_extensions_page](https://cloud.githubusercontent.com/assets/7805635/3869486/c9f9a1c0-2092-11e4-9e22-14d660b05cd9.png)