Issue302

This is my proposal for #302 

![capture du 2014-09-16 16 06 54](https://cloud.githubusercontent.com/assets/265319/4288295/be8ac4ce-3daa-11e4-8f77-e4882f71ca96.png)

Will require to update the following string in spanish, german and russian: "Alter the current map composition with one of these contexts" (rather than the older "Replace current map composition with one of these contexts")