Added Clear Model functionality

User can now clear the model and is prompted to check if they are sure.
Clearing the model is the same as deleting all the blocks.
Added Incremental Block

Added the incremental source block, which can be used to show the number
of ticks the simulation has had. Added image and found and fixed two
bugs with the tick.
Added Run simulation

Added run and stop controls (with disabling action) and a tick timeout
set in harness core at 10ms per tick