Multi select labels

[TrimmingFool]

The labels in the category list should be multi-selectable like rows in the tables.

Intended behavior: Conjunctive inter-category combination (as before) and disjunctive intra-category combination (new). meta/Ctrl: toggle single label shift: select range of labels meta/Ctrl + shift: extend range selection (from last anchor)

Multi-select containers: container ids: [pstate_cont, plabel_cont, flabel_cont, ptrackers_cont]. Search condition is always true for a container/category if All is selected: actLbls[cont] = [].

(rss (prss_cont) and extsearch are still single-select)

Additional Changes

• theWebUI.switchLabel gets an additional labelType, toggle, range parameters
• Label context menu behavior for different containers is moved to labelContextMenu.
• Improve mutli-select behavior of tables (previously selecting multiple small ranges did not work)