use a single validation error handling function
add one role validation method to be used in child objects
use a validation_error method which also does logging
extend drop target to include the box of servers

Fixes bnc#838662
added methods for validating the existence of a db proposal
allow comma-separated lists as well as space separated ones
extending 'wait for chef' for other states
during node edit, offer user to define intended node role
added network role
network role
show Undecided label for no_role
Merge pull request #787 from mapleoin/comma-split

Got +1 and was tested => merging
Merge pull request #782 from mapleoin/one-role

+1 from me; also got smoketested => merging.
Merge pull request #795 from jsuchome/wait-for-chef

Got +1 and was tested => merging.
Merge pull request #786 from mapleoin/droptarget

Got +1 and tested => merging.
Merge pull request #783 from mapleoin/find-database

Got smoketested, and +1 from me too => merging.
Merge pull request #796 from jsuchome/intended-roles

This got smoketested, and pull requests depending on it got smoketested too. It also got +1, so merging.