Allow local max transaction time configuration to override network wide limits

[pmjanus]

The goal is to have a modified version of nodeos which lets the local config file win instead of the network wide setting. Currently it's already configurable per node (up to the network wide limit).

[pmjanus]

You either modify this: https://github.com/AntelopeIO/leap/blob/cedbc5128d15c1f51400b290ac5562dc6f3b3f78/libraries/chain/transaction_context.cpp#L107-L112 or change the value in chainbase.