Fix display formatting of STAmount
RPC: Improve wallet_propose, deprecate wallet_seed:
* Add master_key, public_key and public_key_hex to wallet_propose's JSON response.
* Report an error if we can't understand wallet_propose's passphrase.
* Deprecate wallet_seed by adding a "deprecated" parameter directing the user to wallet_propose.
Fix RIPD-166:

* Allow RPC commands sign and submit to sign using the regular key.
* Allow command line RPC command submit to take an "offline" flag.
* Mark SerializedObject.getFlags() as const.
Universal flags need to be added to tfAccountSetMask
Tidy up some STAmount and base_uint operations:
* Constrain use of arithmetic operators in STAmount
* Prevent constructor conversion of uint256 to uint128 - make intent clear
* Prevent implicit conversion of uint64_t to uint256
* Prevent implicit conversion of uint64_t to uint160
Update README.md
Small Ledger cleanups and improvements:
 * Remove call to updateHash in LedgerConsensus::accept
 * Correct serialization size in updateHash
 * Add some comments to setImmutable and setAccepted
Optimize composition of HTTP/RPC reply strings
If RocksDB high threads are configured, use them for flushes
Allow range-based for to work on STVector256
Finish implementation of Ledger process/Features logic:
* Defining RIPPLE_PROPOSE_FEATURES enables ledger features
* Reduce dependence on getApp via dependency injection
* Converted uint32 members to use Clock::time_point
* Inject Journal, tidy up classes:
    - Features
    - FeaturesImpl
    - FeeVote
    - FeeVoteImpl
Fix out-of-order initialization
Improve Json::Value special members (fixes RIPD-215):
* Add move special members
* Fix Json::Value::swap
Move .proto and generated sources
Validation timing fixes:
* Log whether consensus built a ledger we already had or were acquiring
* Don't trigger an acquire for a validation for a ledger we might be building
* When we finish building a ledger, try to accept that ledger
* If we cannot accept a built ledger, check held validations
* Correctly set isCurrent for untrusted validations
* Add appropriate logging

This fixes a race condition that could cause spurious and expensive
ledger fetches across the network and delayed recognition of
fully-validated ledger.
Add comments to LedgerHistory
Set version to 0.24.0-rc1
Cleanup nodestore backend classes
* Add README.md (WIP)
* Add missing std::move calls
* Refactor visitAll in backend