Merge #325: Expose Address payload and network properties

cd10c75 Add to_qr_uri() method on Address type (thunderbiscuit)
cbd4424 Add kotlin api-docs for Address.payload() and Address.network() (Steve Myers)
20c31d5 Expose Address payload and network properties (Steve Myers)
616cb21 Update Cargo.lock (Steve Myers)

Pull request description:

  ### Description

  Fixes #319

  ### Notes to the reviewers

  The test data was generated with:
  ```
  bitcoin-cli -rpcwallet="regtest2" -datadir=/tmp/regtest1/bitcoind -regtest validateaddress "bcrt1qqjn9gky9mkrm3c28e5e87t5akd3twg6xezp0tv"
  {
    "isvalid": true,
    "address": "bcrt1qqjn9gky9mkrm3c28e5e87t5akd3twg6xezp0tv",
    "scriptPubKey": "001404a6545885dd87b8e147cd327f2e9db362b72346",
    "isscript": false,
    "iswitness": true,
    "witness_version": 0,
    "witness_program": "04a6545885dd87b8e147cd327f2e9db362b72346"
  }
  ```

  ### Changelog notice

  Added
  - Expose Address payload and network properties.

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

  #### New Features:

  * [x] I've added tests for the new feature
  * [x] I've added docs for the new feature

ACKs for top commit:
  thunderbiscuit:
    ACK cd10c75.

Tree-SHA512: 65a1d550577fd4a35cfeb8fb765002e47e0703ff40fc7a68c07b78bc1ba642d33a0efbdfa8f9322024841ba84d25c0e289294c10ae4c1b4d52eb9beffa3d0e10

Author: notmandatory