Remove traces of Boron logic

Remove traces of Boron logic

+ next-release-tag removal postponed to Carbon
+ csit-list-{stream}.inc instead listing all files
+ ovs-scm argument and git-opflex-ovs-v1 macro removed
+ git-opflex-ovs-v2 hardcoded for opflex openvswitch job
+ packaging VERSION_MAJOR not detecting boron
- removed whole comment block for jobs needing only stream and branch
+ for other jobs, edited examples to nitrogen and oxygen
- Comment for RELEASE_TAG kept with older tags
- packaging DOWNLOAD_URL kept with Boron-SR2 URL, FIXME added
+ Comment on BGP *-all features removed (as they are no longer used)
+ CSIT verify overrides removed for Dluxapps and Iotdm
+ Other CSIT old branch comments removed

Change-Id: I1431344cc5afd98e9e2c680ebaec0d3f3ea76dcb
Signed-off-by: Vratko Polak <vrpolak@cisco.com>