Merge branch 'speed-upgrade' into 'master'

Speed upgrade

/cc @jacobvosmaer @dzaporozhets

See merge request !1134

doc/update/6.0-to-7.3.md → doc/update/6.x-or-7.x-to-7.3.md

-# From 6.0 to 7.3
+# From 6.x or 7.x to 7.3
 
-# GitLab 7.3 has not been released yet!
+This allows you to upgrade any version of GitLab from 6.0 and up (including 7.0 and up) to 7.3.
 
 ## Global issue numbers