docs: XMLRPC API docs for jobs.set_response

Bug: 1127509
Change-Id: I26d5e834115e3c0cde0b1a07a3ab3035c9462bb0
docs: expand description of recipe set ack/nak

Bug: 1127509
Change-Id: I4bc3e507fa48e0e4839eff896fe0a238104c60ec
use OSMajor.default_install_options for VirtResource and GuestResource

Bug: 1138533
Change-Id: Id2eb4226d8c6289331592fbeab9b540d618d5912
use OSMajor custom install options for VirtResource and GuestResource

Bug: 1139951
Change-Id: Ibd6fd95cfc2e62c584ecbe09c2f36b2fea86852d
add bz950903 to 0.18.0 release notes

This was accidentally omitted since the patches didn't have
a documentation/whats-new/next/* file and the Bugzilla milestone was not
set correctly.

Change-Id: I0fbcd6de338572d4c85f89f2cf0f10979531832d
release notes for 0.18.1

Change-Id: Ic7dc1c63869ca2db9e72eee44172694015d8192c
Automatic commit of release 0.18.1
Merge branch 'develop' into new-system-page