Major refactoring on the windows installer scripts

I know that this is a pretty big patch. So I will start with what I want you to pay extra attention to.

1. I have to use 2 third party NSIS plugins. I have included them inside the folder "nsis plugins" (for fearing that they might go missing from the official site). I think that their licenses are compatible with qbt's. Please double check. Although I think that the scripts can be under an entirely different license than the qbt source IMO.

2. I have added some more info to be embedded to the installer executable. This is taken from the qbittorrent.rc file. Please take a look in this [commit](https://github.com/sledgehammer999/qBittorrent/commit/e71facf6d684052a6442810f2b5a203f418fbd65).

3. Also I add some more info to the system for the installer. Please take a look in this [commit](https://github.com/sledgehammer999/qBittorrent/commit/c13776d000f04575c4ca772c65e87f8a39b44bc6).

Feature list(for the changelog):

* Support translation for every string used in the installer.
* Ability to add an exception to the windows firewall.
* Option to remove configuration files during uninstall but keep cached torrents and vice versa.
* Add version info to the installer executable.
* Add more info to the system about the uninstaller.
* Offer to launch qbittorrent after installation.
* Check if qbittorrent is running before installing/uninstalling.
* Run uninstaller silently just before actually doing the installation.
*  Remove file associations only if qbittorrent is associated. Fixes issue #307.