Implement a flag to skip transaction validation

[bluesign]

Issue To Be Solved

Currently in many use cases (playground, testing etc) there is a need to skip some verifications in transactions. Signature, Proposer sequence number etc

Suggest A Solution

some flag like --skip-tx-validation which will allow to bypass signature checks would be really useful.

Context

I am building a playground backed by emulator.

cc: @sideninja