Create plugin sample

[imago-storm]

From @lrochette on December 11, 2015 13:1

Create an example that download a plugin from GitGub
Install it
Promote it

Copied from original issue: electric-cloud#19

[imago-storm]

From @lrochette on December 11, 2015 15:28

issue with installPlugin:

def _url = 'https://github.com/electric-cloud/EC-Admin/blob/master/EC-Admin.jar?raw=true'
def resp=installPlugin(url: _url)

Unknown exception during DSL eval at line 26: All nested operations must support requeuing: installPluginOperation does, but context[op=evalDsl,id=13350] doesn't
Line 0026: Method 'installPlugin'
Line 0026: Invoking 'installPlugin' with args {url=https://github.com/electric-cloud/EC-Admin/blob/master/EC-Admin.jar?raw=true}