Add simulation to the escrow module

[LeCodeurDuDimanche]

Complete the simulation interface to the escrow module to be able to use the cosmos-sdk simulation capabilities

[LeCodeurDuDimanche]

For now, the escrow module cannot work without the configuration module and the simulation needs escrows creation to happen to be useful, so we need to simulate escrow creation in the starname module as well.
We thus need to implement simulation in the configuration (just the genesis is needed) and the starname modules if we want a working and meaningful simulation for the escrow.