Qt metrics v1.5: URL encoding

Ajax Get method cannot pass special characters like plus sign in the URL.
Previously a character manipulation solution used, now replaced with a
proper PHP and JavaScript function calls. This is pure implementation
issue and is not visible to the user.

Change-Id: Idabd1dddd82a161b4695a8b234c2a055d77ab2f7
Reviewed-by: Tony Sarajärvi <tony.sarajarvi@digia.com>