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
Constrain use of arithmetic operators in STAmount
[FOLD] Prevent implicit conversion of uint64_t to uint160
[FOLD] Prevent implicit conversion of uint64_t to uint256
[FOLD] Prevent constructor conversion of uint256 to uint128 - make intent clear