SD-657 : Text content-item autosaving
SD-657 : Text content-item autosaving
feat(comments): add comment id and item id in activity

to be able to add a link to item and comment from notifications tab
we need item id and comment id to be part of activity.

SD-722
fix(cors): set max age for cors headers

this will make client cache preflight requests
Merge pull request #271 from petrjasek/feat-comment-activity

feat(comments): add comment id and item id in activity
spike(services) - introduce services and injected data layer.
spike(services) - update preferences to use BaseService class
spike(services) - create only one instance of EveBackend
spike(services) - rename BaseModel to Resource, move all methods from
Resource to datalayer.py. Renamed endpoint_name to datasource in
BaseService.
Rebase from master, fix item lock and autosave.