splinter: Port to GnomeAttachmentStatus
template overrides: Minimize changes in attachment/edit override

Introduce a hook that will be used by GnomeAttachmentStatus extension.
attachment status: Implement a hook to show a combobox with statuses

We use the new editable_hidden_content hook from attachment/edit.
splinter: Remove TODO comments

Their place is in TODO file.
weekly bug summary: Remove TODO comments

Their place is in TODO file.
TODO: Update
patch report: Fix interval computations

sql_interval is probably a remnant from 3.6. Closest thing to it I
could find is sql_date_math.
patch report: Add a GNOME specific open bug statuses getter
browse: Use gnome_open_statuses for open bug statuses

So the results here are consistent with PatchStatus extension.
weekly bug summary: Use gnome_open_statuses for open bug statuses

Also, add a dependency on PatchStatus.
trace parser: Use proper filter

url_quote filter does not exist in Template Toolkit. Maybe it existed
in previous major version. Replaced it with plain url filter.
TODO: Update