Integrate namespaces

This integrates namespaces in the installer and the three Fork applications. These are the reasons to do it:

* Avoid custom autoloaders
* Move to more standardised/modern code
* Take a step closer to integrating other libraries (such as doctrine)
* Test all core/modules code again to make sure everything works

The installer and all frontend actions, widgets and ajax actions have been tested and work correctly
This is the list of all tested backend actions:
https://docs.google.com/spreadsheet/ccc?key=0ApSZdWn75FMWdDBxVVlaaElEQVVySDN1VFFxUko1b2c#gid=0

The documentation has been updated here: https://github.com/forkcms/documentation/pull/19

### To test:

* Analytics: there's a bug in the core. (fixed in #631) Running the cronjob for getting data works when I execute the url manually. The curl call in the Loading.php action doesn't seem to work though (locally and in sneakers) All analytics actions depending on this one aren't tested because of it.

### Bugs in the core

These are some bugs that are still available in the core of Fork (and that aren't caused by the namespaces)

* CommonUri::GetUrl removes greek (and probably other UTF-8) characters from url's. This should only be done when creating filenames, not url's
* Analytics: the curl call to the getData cronjob in Loading.php doesn't seem to work (locally and in sneakers) @dieterve Does this work locally?

### What has still to be done

* Add namespaces to new commits in the master since the creation of this branch
* Poke module devs to tag their modules as stable 3.6 and update them to the namespaced versions.