Add tests for the StepIterator class
Rewrite image selection to use StepIterators

OdtDocument.getDistanceFromCursor is no longer used by any code.
Rewrite some cursor move & extend actions to use a StepIterator
Simplify PositionFilterChain to not use named filters

PositionFilterChains no longer have any need to allow adding or removal
of named filters. In practice, filters are only ever added just after
construction, and remain unchanged beyond this point. This allows a
slight simplification of the PositionFilterChain interface.
Simply logic in OdtDocument.createStepIterator
Merge pull request #315 from peitschie/migrate-step-iterator

Rewrite some selection features to use StepIterators
In edit mode, only open a hyperlink with Command+Click on MacOS

This matches the behaviour of LibreOffice.
Respond to ctrl key press event in edit mode only.
Stops FireFox from opening two new tabs upon ctrl/cmd + click a hyperlink

Fixes issue #70 and partially for #69 by prevent browser default action.
In edit mode, resets hyperlink cursor style to text whenever the editor got focus.

This prevents the cursor stays as hand icon in case user release the ctrl key after the editor lost focus.