Support stop/reset deployment mechanism

* Add ability to stop deployment by request;
* Add ability to reset deployment by request;
* Small refactoring.

Implements: blueprint fuel-stop-deployment
Implements: bluepring naily-reset-env

Change-Id: Idbf7a4a00187edf8ab97fa3a41d724a55135d415
Implementation of stopping/resetting env in Nailgun

Added implementation of environment resetting

Change-Id: Ib2c8d2f7f570ba4293f7930cf4837a7ec09e222b
Stop/Reset actions on UI

Change-Id: Ib2df1cf52a135bdac14e71a2684c3f54d3987620