ReqMgr2 request injection extended, polished

-this patch depends on what comes in request/spec arguments validation in
    #4705
-validation of RequestName, software, scramarch added
-ReqMgr2 derives Requestor automatically, if a user specifies Requestor field
    it fails to inject (fixes 4238)
-Scenario should be removed from from ReDigi, ReReco templates after #4705
-all 10 request templates can now be injected to both ReqMgr1, ReqMgr2

This should go into July deployment of ReqMgr2.

@ericvaandering please review.
Merge pull request #4707 from zdenekmaxa/reqmgr2-request-injection-2

ReqMgr2 request injection extended, polished
0.9.78

Signed-off-by: Zdenek Maxa <zdenek.maxa@cern.ch>