Acoustics, BlockMap and Solver are now running in a context (this eventually allows multiple instances of Isolators to run):

- Added BlockMap to store BlockMap data
- Created PropertyBlockMap_Engine0 to load BlockMap files
- Solver is now contextualised within an isolator
- Removed useless interface VariableGenerator
- The PFIsolator is now the variator that will propagate the Variator to its context