Message support for thin provisiong

Message support for thin provisiong

lvm part of messaging.

Each message is now stored it's own thin pool section:

message1 {
	create = lv
}

Messages are queued to thin pool dm target when this target
is going to be resumed or used through some dependency.

Currently  'delete' message are purely queued and processed
with next thin pool resume operation (i.e. create_thin).

WARNING - thin provisioning support is developmental code.