Added a batchscript for OpenRA.Utility.exe

To make using OpenRA.Utility.exe more convenient for win users.

Looks like this:
At first you'll be asked to choose a mod:
![utilitybat1](https://cloud.githubusercontent.com/assets/7704140/4651419/c588cc1e-549b-11e4-80e5-5b69ad3da6a1.png)
Invalid mods aren't permitted:
![utilitybat3](https://cloud.githubusercontent.com/assets/7704140/4651431/d71b3ea8-549b-11e4-8162-4c931b62bac5.png)![utilitybat2](https://cloud.githubusercontent.com/assets/7704140/4651427/d1e82126-549b-11e4-8049-6025af2ed180.png)
Then you can use it:
![utilitybat4](https://cloud.githubusercontent.com/assets/7704140/4651465/19b2e6ee-549c-11e4-8ed6-78eb7ca9bf8c.png)
![utilitybat5](https://cloud.githubusercontent.com/assets/7704140/4651657/c3c03136-549d-11e4-81dc-5b93c8b8aef7.png)
etc...





typo:

```diff
-avialable
+available
```