Refactored online installer/uninstaller

Before the version 0.1.0, I've already created a "online installer/uninstaller".
With this feature, anyone can install CentralReport on his host with a simple command in a terminal, without downloading the project before.

In the idea, you open the terminal, and you copy/past the following command:
```bash
curl http://scripts.centralreport.net/install | bash
```
(This URL doesn't exist yet, but it will be the "tools/online_installer.sh" script)

This script...
* Checks the current OS
* Checks if Python is available
* Downloads a "full package"
* Unarchives the full package
* Updates the chmod on install.sh script (chmod +x install.sh)
* Executes the install.sh script
* Deletes the unarchived package
* Deletes the package downloaded

The full package must be generated before with the "tools/packager.sh" script.
This packager generate an archive (.tar.gz) with the complete CentralReport script (as you download it manually from Github in the master branch).
It must be available from the centralreport server, and the URL fixed in online installer and uninstaller.

With this feature, installing or deleting CentralReport from any host connected to Internet will be easy.

(PS: the same solution exists also for the uninstaller)