add file foreign key to property model
add files to entity api
serialize file as integer id
add file_url item to property data
model for image configuration
add image config relation on files and attributes
transform images
local file 'uploading' works
rename logic.image => logic.images
validate + save/update logic for ImageConfig
Merge branch 'master' into images

Conflicts:
	grano/logic/schemata.py
merge DB migrations
filter out properties without a file attached
get rid of image logic in grano - moved to grano-images
Merge branch 'master' into images

Conflicts:
	grano/logic/properties.py
merge branched migrations
missed merge conflict
issue #72 fix
handle saving existing file properties correctly
issue #72 fix