Prepare version to be v1.21.0
Prepare version to be v1.21.0

Since `fog-core` versions will predate `fog` versions and the next
version would be v1.21.0 so this allows us to reference the correct core

Temikus/fog-core,higanworks/fog-core,SpryBTS/fog-core,fog/fog-core,Ladas/fog-core,mdarby/fog-core