MDI History Improvements to delete functionality

[joco-nz]

Changes:

• Changed delete row to delete selection. It will delete all selected items.
• Added method to delete all entries in history
• Added remove all to Status plugin to back up adjustments to mdi history
• Fixed the todo list and a spelling mistake
• Changed comment string in clearQueue to be more explicit as to what is happening

Tested on my UI and behaviour seems solid.

Code should also be able to be merged into the python2_maintenance line. But a peer review to ensure no py2 v's py3 issues exist would be appropriate.

[TurBoss]

Thank you so much!