* Add sending and receiving features and enable them by default
* Add feature attributes in code and tests
* Add serde as dev-dependency
* Small improvements to sending docs
* Copy recipient code structure from Sosthene00 fork
* Move SilentPayment struct to receiving
* Provide shared_secret as input argument for scan_for_outputs
Also refactors a number of things to enable this change: calculate A_sum
and outpoints_hash in the test code instead of the library, remove the
obsolete hash_outpoints function from the library move calculate_P_n
and calculate_t_n to utils.rs.
* Add debug trait implementation for Label
* Refactoring
* Add get_receiving_address function for getting sp-address per label
* Refactor scan_for_outputs and rename to scan_transaction
* Provide tweak data to scan_transaction function
* Expand README.me
* Refactor tests: add utils.rs for test helper functions
* Refactor sending
* Add SilentPaymentAddress struct
* Use structs instead of tuples as func arguments
* Change create_outputs function and remove amounts
* Use is_testnet in SilentPaymentAddress struct
* Provide pre-computed tweak data to create_outputs function
* Git rebase main
* Provide ecdh shared secret as argument to create_output
* Rename create_outputs -> generate_recipient_pubkeys
* Remove all references to input.rs from other files
* Move test vector test to integration test folder
* Move test vector file into integration test folder
* Move input.rs to tests folder
cygnet