Remote execution on slaves + some changes

+ Adding remote execution everywhere. Affected areas are updating
controller; adding agents; installing agent; fetching agents.xml and
environments.xml from correct slave to leroy node config page/leroy
builder step; runnning configuration job and deploying job
+ LEROY-449 - adding a message but not button to check controller version
again
+ LEROY-473
+ LEROY-464
* refactor a bit, removed unused files, reduced the size of plugin from
* ~1.5Mb to ~800Kb