Extend The Script Language

[dangershony]

Some networks made changes to the scrip language (like strax adding federation masternodes and a new opcode)

Right now we are sort of no allowing to extend script without some complex flags (see cold staking activation)
I think it could be a good idea to allow to inject classes that can override some opcodes and put those in the consensus class (like we do with the rules)

This will allow to be fully compatible with strax but also extend opcodes for other networks