add uwsgi provider for WSGI applications
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
Merge pull request #777 from MirantisDellCrowbar/feature/uwsgi/master

[feature] add uwsgi provider for WSGI applications
timeout must be integer
remove comment from xml config
Merge pull request #799 from MirantisDellCrowbar/bug/uwsgi-config/master

remove comment from xml config
Merge pull request #798 from jsuchome/timeout

timeout must be integer
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.