Improve import of Random Groups and Custom Blocks

I suggest the following:


- Distinguish between Global and Strategy Specific customizations.
- The "global" Random Groups and Custom Blocks are stored at the application level, and only change when they are edited. 
- The "strategy specific" Groups and Blocks are imported each time you load a strategy, and they just replace what was previously there. 


It is understood, then, that if you want to keep your customizations for all strategies to use, you place them at the global level, and if you want to create strategy specific customizations, you can do that as well.


As a polishing feature, you might make it easy to move customizations between "strategy specific" scope and "global" scope.