ReqMgr2 project startup

-REST service based on WMCore.REST (new REST API)
-some example plus request list, query REST API
-configuration defined, called from deployment/reqmgr2/config.py
-startup of web GUI implemented in JavaScript, calling service's REST APIs
-couchapp ReqMgr (after initial clean up remained 1 view) shared between
ReqMgr1 and ReqMgr2 (validation, update already previously implemented),
necessary view will be addded
-CouchDB database (reqmgr_workload_cache) behind, shared with ReqMgr1

Incorporated comments from @ticonn collected on #4542
Incorporated comments from @geneguvo:
    -only 1 major config.py under deployment
    -regexp exported into a dedicated module

Added a check in WMCore.REST.Main, since it relies on private patched version
of cherrypy.
Merge pull request #4555 from zdenekmaxa/reqmgr2-startup-2

ReqMgr2 project startup