TTL Implementation (#261)

* refactor address generation code into libwallet, bool to flag whether to include proof, add sender address in init_send_tx

* rustfmt

* require payment proof addr as part of init_tx

* rustfmt

* store payment proof on sender transaction side

* rustfmt

* change sig to ed25519 sig

* rustfmt

* add message creation and signature

* rustfmt

* add payment proof verification function

* rustfmt

* validate proof on sender side, store proof

* rustfmt

* fix json tests

* fixes and updates to tests

* added API functions for converting and retrieving proof addresses

* rustfmt

* add payment proof to init_send_tx example

* rustfmt

* incorrect comment

* add commands for requesting payment proofs

* rustfmt

* wire up payment proofs into command line

* rustfmt

* add address command

* rustfmt

* added tor sending from owner api

* rustfmt

* add TTL to slate, transaction log

* ttl cutoff tests

* add ttl check to recieve functions, add tests, modify doctests

* rustfmt

* fixes from upstream changes and test fixes

* rustfmt

* remove unnecessary block header version check

tests/data/v2_reqs/init_send_tx.req.json

@@ -12,6 +12,7 @@
 			"message": "my message",
 			"target_slate_version": null,
 			"payment_proof_recipient_address": null,
+			"ttl_blocks": null,
 			"send_args": null
 		}
 	},

tests/data/v3_reqs/init_send_tx.req.json

@@ -13,6 +13,7 @@
 			"message": "my message",
 			"target_slate_version": null,
 			"payment_proof_recipient_address": null,
+			"ttl_blocks": null,
 			"send_args": null
 		}
 	},