[backend] be more verbose about unfinished prps
[backend] log event processing
[backend] fix bad ping call
[backend] ask correct server for preinstallimageinfos
[webui] working on random code issues rubymine complained about
[webui,api] make sure target_maintainer is set correctly

(part of issue#395)
[dist] revert thinking_spinx back to 3.0.4,

ancor will check what's the problem with 3.0.5 later, but for now having
a stable travis outcome is more important
[api] rename 997 to 1