* remove context object from aggsig and transaction libs
* fix to aggsig, and remove unnecessary warnings
* put tx_fee function into libwallet::transaction
* Error cleanup, and creating libwallet error type
* remove some unwraps
* checker bug
* ensure transaction tests checks sender's wallet
* Beginning to rework aggsig library workflow
* more refactoring of transaction api
* whoever does round 1 first creates offset
* slate finalisation now context-free, so anyone can do it
* remove concept of transaction phase
* remove slate phase enum
* update actual send/receive code with new transaction lib workflow
* 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
