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.
Merge pull request #317 from kevinlli/hyperlinkImprovement

Address a few hyperlink related issues