* refactoring transaction building code
* serialise return transaction
* move shared functions into transactions, ensure wallet manipulation is only done outside of aggsig transaction lib
* remove unneeded wallet config from fn
* adding test functions to facilitate libwallet transaction testing
* rustfmt
* refactoring checker somewhat, adding ability to create and transactions against local copy of chain for simpler testing
* finish transaction testing functionality which verifies transactions work properly
* Remove wallet output manipulation from transaction building lib
* ensure sender expects full transaction back on last phase
* ensure sender expects full transaction back on last phase
