Include isolate using a git submodule

Since there is an isolate repository under the cms-dev organization, maybe it makes sense to include it as a submodule (instead of copying it on every update). This way would avoid code duplication, wouldn't it?

Note that, apparently, the isolate repository is not up to date with the current isolate folder in this repository (for example, there is no compile.sh). So, if you want to merge this PR, then probably you should first update cms-dev/isolate.