Better handle of filter destruction

This commit enable a better filter and sorter handling.

While a sorter is destroyed (often in QML context), it will trigger
a resort of the visible data.

While a filter is destroyed, it invalidates all the cached data
for nodes that used that filter. It is rather dangerous to
destroy filters dynamically, since there would be data-loss in the
cache. So it is better to destroy them if we know that we will
never use a node again, or do not destroy them at all.
WIP: begin adding Twitter social network adaptors

Stage one: create Twitter SNI adaptor
    - almost complete
Stage two: create Twitter content item subtypes
    - not started
Stage three: create Twitter filters/sorters
    - not started
Stage four: write tests
    - not started
Initial work on Twitter

Relayout of tools
Test twitter app with pin based auth
Added fixes for Qt5
More work on twitter test
Initial work on TI
More work
More work