Freeze enforcing: (RIPD-399)
 * Set enforce date: September 15, 2014
 * Enforce in stand alone mode
 * Enforce at source
 * Enforce intermediary nodes
 * Enforce global freeze in get paths out
 * Enforce global freeze in create offer
 * Don't consider frozen links a path out
 * Handle in getBookPage
 * Enforce in new offer transactors
Remove TRUST_NETWORK directive (RIPD-331)
Add pubkey_node and hostid to server stream messages (RIPD-407)
Remove LedgerBase and decongest Ledger locks
Detect inconsistency in PeerFinder self-connects (RIPD-411)
HTTP support improvements:
* RFC2616 compliance
* Case insensitive equality, inequality operators for strings
* Improvements to message_parser
* Tidy up HTTP method enumeration
* boost::asio buffer helpers
HTTP handshake in peer protocol (RIPD-351):
* New I/O paths for client and server role
* New handshake_analyzer detects the peer protocol
* New basic_message class for parsing and storing HTTP messages
* Conditional compilation for selective feature enabling.
* Server supports both current handshake and HTTP handshake
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