Speedup

• Boost synchronization speed. (It nows syncs in 15-20 minutes to the latest checkpoint. If you want to sync even faster, take the most recent block's height and hash and feed it to daemon as a checkpoint with --load-checkpoints flag)
• Code cleanup: removed various unused files and functions, fixed some bugs
• Changes in RPC: removed some deprecated methods, renamed some fields (many that should've been changed too were left intact for backward compatibility with wallets), allowed some methods while node is syncing
• Check locked amounts in reserve proof RPC method
• Start scan height option for restoring wallets
• Functions used in GUI to lock wallet and to confirm sensitive operations by password
• Daemon save command to store blockchain cache to disk
• RPC method for walletd to show addresses count