* make transaction field in V4 Slate optional
* add mutable/non mutable version of tx getter
* removal of mut references where not needed
* remove more muts
* update from master
* update from master
* test fixes
* initial addition of ov3
* move libwallet address functions into OnionV3Address type
* incorporate OnionV3 type where possible
* factor out manual dalek pubkey manipulations
* corrections due to test failures
* change json-rpc example to use ov3 for payment proof recipient address
