Added better support for masternode configuration file and rpc commands.

masternodeconfig provides class to handle masternode configuration
masternodeconfig reads configuration upon init
new masternode rpc commands: stop-many, start-alias, stop-alias, list-conf. Only list-conf functional at this time.
Initial code cleanup.

Reviewed activemasternode fields
Added notCapableReason field for better handling not capable issues
Code cleanup
masternode: fix dseep DoS

When a dseep message with an invalid signature is received, the
lastDseep timestamp is updated to sigTime, but the message rejected.
Further messages with a sigTime before lastDseep will not be
processed, meaning the LastSeen timestamp will not get updated.

By disabling dseep processing for more than 65 minutes an attacker
can cause a master node to time out.

Only update the lastDseep stamp if the message is signed with the
correct key.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Refactored and implemented start-many, start-alias, stop-many, stop-alias
Merge branch 'master' into start-many-enhanced
Further cleanup and corrections of CActiveMasternode