Merge: remove "checkorder" and "reply" P2P commands

These command are a leftover from send-to-IP transactions, which have been
removed a long time ago.
Also removes CNode::mapRequests and CNode::PushRequests, as these were
only used for the mentioned commands.

Conflicts:
	src/main.cpp
	src/net.h

Conflicts:
	src/main.cpp
	src/net.h