[META] Untangle office_hours

Issue to keep track of several interdependent issues to consolidate office_hours.

These should be commited in order because the patch in each was built upon the others:

* #1912996: Move hook_field_schema() to .install
* #1912998: Fix usage of default values in hook_field_settings_form()
* #1913008: Disable field settings once it has data
* #1913010: Fix formatter definition
* #1913018: Rename office_hours form element to office_hours_slot.
* #1913030: Transform _office_hours_return_defaults() into office_hours_select element's value_callback
* #1913034: Calculate valid hours and minutes intervals at the field widget level, not the form element
* #1168126: Default value for every day of the week
* #1913990: Convert formatter to new internal data structure
* #1914002: Convert db schema to day+daydelta