Move crowbar_node and crowbar_data out of ChefObject

These methods are specific to NodeObject and ProposalObject, so they
should not be inherited by other classes.

They were used only on two other places, so move them over to where
they're called.
Add 'interface' tests to *Object finders

These tests should ensure that all barclamps still call existing methods
if the finders are ever refactored.
Removed useless file
Replaced all license headers with unified layout
Added missing inline documentation parts for barclamp model
Merge pull request #1040 from bkutil/move_chef_loaders_out

Move crowbar_node and crowbar_data out of ChefObject
Merge pull request #1044 from tboerger/feature/model-documentation

Added missing inline documentation parts for barclamp model
Merge pull request #1042 from tboerger/feature/license-header

Replaced all license headers with unified layout
Making present become the past to not predict the future
Merge pull request #1041 from bkutil/add_finder_tests

Add 'interface' tests to *Object finders