Refactor views into multiple files prior to developing edit item features. Also changed the edit/create item urls.

Only display the Remove Question Type menu item on pages where the
question type can be set.

Ideally I'd like None to represent no category but empty string fits
better with what is on the form for the individual dropdowns. So
let's make that consistent.

Message -> Item and Category -> Question Type

If there is no source set on the tab configuration, the upload
button will no longer be displayed.

Added network_provider column to ItemTable, and ensure it's not displayed in the table widget. Also ensure the widget doesn't display the 'select_item' column, previously named 'delete'.

So user is redirected to the correct page after uploading data

When process_items is called without a request, redirect to data-view (don't try to double guess the tab)

Provide the tab instance to get_context_data, and use that to work out the URL to redirect forms to.

Remove outer html from the view and edit page, this is now taken care of by the tabbed page rendering.

Refactor the ViewsItems view, which covered the view and edit table, into a separate (non-view) class under tabs/view_and_edit_table.py. When ready, this will plug straight away into the new tabbed page functionality - in the mean time there is a place holder view to display the view where it used to be found.

Ensure we use the right taxonomy for the question category. The taxonomy in use is still hard-coded, as that is something we will look at later - this commit was only intended to restore functionality to the existing level.

There are two new item types 'question' and 'rumor'.
Item types for GeoPoll data are 'question'.
Item types for RapidPro data are 'rumor'

Allow the chart count widget to have a time period. When present, apply the time period and display a legend detailing what the time period is.

-- replaced {{name}} with {{title}} on chart widget template
-- added h2 tag around bar chart table template title
-- fixed icon span class

ViewItem.get_category_options should return the options as we want them - we shouldn't have to process them later. So make sure it returns (short question, short question) as we want both the value and the text to use the short version.