NOBUG admin page that lists contexts and categories

and the number of questions contained in them.
Merge branch 'wip_imagetargetconverter_2_1' into wip_imagetargetconverter
NOBUG further work on adminpage
Merge branch 'wip_imagetargetconverter_2_1' into wip_imagetargetconverter
NOBUG change API calls that only work post 2.1

This need to be merged into master branch because we want to keep the
2.1 branch mergeable but then we will merge with 'ours' strategy,
effectively discarding changes.
Merge branch 'wip_imagetargetconverter_2_1' into wip_imagetargetconverter
NOBUG fixing coding style deviations found by code checker.
Merge branch 'wip_imagetargetconverter_2_1' into wip_imagetargetconverter
NOBUG fixing white space issue
NOBUG list questions in categories in category / context selection UI
Merge branch 'wip_imagetargetconverter_2_1' into wip_imagetargetconverter
NOBUG fixing error in sql to fetch relevant questions
NOBUG restructuring if conditions to interpret page params
NOBUG adding method to process questions.
NOBUG moved list classes to new file
NOBUG some fixes to php doc comments
NOBUG subclass list and list item classes to add specific processing
NOBUG loading imagetarget and answers records all before processing
NOBUG make it possible to select just one question for processing
NOBUG improvement in wording of messages for the user