Improving CentralReport security and integration on operating systems

This pull request will change many elements in CentralReport. Summary:
- [x] Adding a system user to secure CentralReport daemon.
- [x] Adding a launch script in /usr/local/bin, which will be included in the PATH.
- [x] All python modules will go to /usr/local/lib.

Now, with details:
## CentralReport user
For the moment, CentralReport is executed with root permissions. It isn't really secure, we can't say otherwise. So, to secure scripts, CentralReport will have his own user, with only few rights in the system.
- [x] Make some research
- [x] Add the new user on Debian
- [x] Add the new user on Mac OS
- [x] Update all install/uninstall functions
- [x] Update rights on /usr/local/lib/centralreport (see "Launch script")
- [x] Make a new folder in /var/log and update rights
- [x] Make a new folder in /var/run and update rights
- [x] Update documentation

## Launch script
For the moment, we must start or stop CentralReport with a long command: ```sudo python /usr/local/bin/centralreport/centralreport.py start```. Yeah... Boring.
By adding a new script, it will be easier. The new command can look like: ```centralreport start```. Better, no?
- [x] Creation of the new binary script (CentralReport user is required)
- [x] Update install and uninstall bash scripts for all OS (copy, delete and chmod +x)
- [x] Update init script (init.d for Debian and LaunchDaemon for Mac)
- [x] Update documentation

## Python modules
Put all python scripts and modules in /usr/local/lib is more logical according to me.
- [x] Update all bash functions (install/uninstall)
- [x] Update documentation