Data API v2.2 (#193)

* data api 2.2 - ported docs from upstream (some edits)

* Data API v2.2 - some cleanup, API tool methods (incomplete)

* Data API v2.2 - more cleanup (draft done)

* Data API v2.2 - minor cleanup

* Data API tool - fix 'a transactions' typo

content/data_types/public_key.md

@@ -0,0 +1,13 @@
+The Ripple Consensus Ledger (RCL) uses public keys to verify cryptographic signatures in several places:
+
+* To authorize transactions, a public key is attached to the transaction. The public key must be mathematically associated with the sending Ripple address or the sender's regular key address.
+* To secure peer-to-peer communications between `rippled` servers. This uses a "node public key" that the server generates randomly when it starts with an empty database.
+* To sign validation votes as part of the consensus process. This uses a "validator public key" that the server operator [defines in the config file](tutorial-rippled-setup.html#validator-setup).
+
+Validator public keys and node public keys use the exact same format.
+
+Public keys can be represented in hexadecimal or in base-58. In hexadecimal, all three types of public keys are 33 bytes (66 characters) long.
+
+In base-58 format, validator public keys and node public keys always start with the character `n`, commonly followed by the character `9`. A validator public key in base-58 format can be up to 53 characters long. Example node public key: `n9Mxf6qD4J55XeLSCEpqaePW4GjoCR5U1ZeGZGJUCNe3bQa4yQbG`.
+
+Ripple addresses are mathematically associated with a public key. This public key is rarely encoded in base-58, but when it is, it starts with the character `a`.