Improve & refactor interactive tutorial code

Interactive tutorials: more consistent style

Interactive tutorials: Use new generics for send-xrp, use-tickets

Interactive tutorials: clean up now-unused code

Interactive tutorials: progress & debugging of errors

Interactive: Require Destination Tags; and related

- Validate addresses in Transaction Sender and warn on Mainnet X-address
- Option to load destination address from query param in Tx Sender
- Some more/updated helpers in interactive tutorial JS

Interactive tutorials: fix JA version

Interactive tutorials: readme, include code filter (incomplete)

Interactive tutorials: improvements for consistency

Interactive Tutorials: finish readme

Interactive tutorials: fix syntax errors

content/_snippets/interactive-tutorials/generate-step.md

@@ -0,0 +1,15 @@
+{% if use_network is undefined or use_network == "Testnet" %}
+  {% set use_network = "Testnet" %}
+  {% set faucet_url = "https://faucet.altnet.rippletest.net/accounts" %}
+{% elif use_network == "Devnet" %}
+  {% set faucet_url = "https://faucet.devnet.rippletest.net/accounts" %}
+{# No faucet for Mainnet! #}
+{% endif %}
+
+{{ start_step("Generate") }}
+<button id="generate-creds-button" class="btn btn-primary" data-fauceturl="{{faucet_url}}">Get {{use_network}} credentials</button>
+<div class="loader collapse"><img class="throbber" src="assets/img/xrp-loader-96.png">Generating Keys...</div>
+<div class="output-area"></div>
+{{ end_step() }}
+
+**Caution:** Ripple provides the [Testnet and Devnet](parallel-networks.html) for testing purposes only, and sometimes resets the state of these test networks along with all balances. As a precaution, Ripple recommends **not** using the same addresses on Testnet/Devnet and Mainnet.