Add missing mine symbols

I noticed in the 2525D spec that there are a couple of mine warfare symbols that have an alternative icon defined, but no medal icon (see also issue #118). I don't know why this is the case .

The pull request adds the missing svgs based on the alternative icons and updates the instance file. 

I fully understand if you don't want to accept this pull request because it deviates from the official spec. Feel free to close it. If you have contacts at DISA, maybe you can ask them about the missing mine symbols? 

![image](https://cloud.githubusercontent.com/assets/29217/5172521/fe7d68dc-7420-11e4-8df9-c37a28c1d7d1.png) ![image](https://cloud.githubusercontent.com/assets/29217/5172509/ec2c148a-7420-11e4-81ef-0d8dfcf2b036.png)