bitbake: toaster: toastertables REST refactoring

bitbake: toaster: toastertables REST refactoring

This patch refactors the ToasterTables to bring them in line
with REST principles -

- all table pages now support the "format=json" GET parameter
that returns the data in JSON format
- the tables themselves

This cleans up the URL namespace by aleviating the need to
have two URLS for each table (one for the template and one for
the data loading), and fixes minor things in the ToasterTable
implementation.

(Bitbake rev: 1778dac9fd39dae75c55bf2cf836cdd488dbc265)

Signed-off-by: Alexandru DAMIAN <alexandru.damian@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>