Less use optimisation

Improvement:
* LESS file watcher (using the command `grunt dev`, this command also start the web server and open page preview)
* Add LiveReload support (using the command `grunt watch:css` or include in the command `grunt dev`)
* Add deployement tool (using the command `grunt deploy`, this will be useful once we have a hosting server...)
* Add production version preview (using the command `grunt prod`)

To test this PR, see the README.md file to configure correctly the project.

**You will need to create a file name serverConf.json to be able to run grunt. Jsut paste this in it this:**

```
{
	"host": "server.com",
	"port": 21,
	"authKey": {
		"username": "username1",
		"password": "password1"
	}
}
```
I don't include this file in the repo because it will contain information to access to the web server.