CMDB API extensions

POST requests to CI - sending JSON object formatted the same way as obtainable via GET request will result in creating new CI (Configuration Item) in CMDB database. This call supports specifying multiple types, layers and owners - by default this will create relations between newly created CI object with needed CIType, CILayer and/or CIOwner objects identified by supplied “id” attribute. If “id” is not specified in JSON document extension will try to create and link needed new resource object using other details (“first_name”, “last_name” and “email” for CIOwner, “name” for CILayer) from JSON document.
POST request to CIRelation - sending JSON document with two fields - “parent” and “child” containing ids of two existing CI objects will result in creation of CI Relation between those CIs with correspondent parent-child roles.
Hotfix for venture add form
Merge pull request #703 from zefciu/master

Hotfix for venture add form
Fixed the bug with new relation validation
Merge pull request #705 from zefciu/fix-relation-form

Fixed the bug with new relation validation
Incorporated suggestions from inc0
Removing the link from assets when deleting the device
Merge pull request #710 from zefciu/master

Removing the link from assets when deleting the device
Merge pull request #701 from frank-borkin/master

Merging. In the future, please merge to 'develop' branch to conform to our standards.
Merge branch 'master' into develop

+ Fixed the test broken by delete feauture

Conflicts:
	src/ralph/cmdb/forms.py
	src/ralph/discovery/models_device.py