Improvements & consolidations to position display

[crazyscot]

• Bugfix: defer initial output of position display for correctness
• Redesign HUD & position entry form: default to Centre, with a menu item to flip to Origin mode
• Add close (X) controls to HUD and position entry form
• Remove menu checkmark on Go To Position
• Add Copy Current Position to data form
• Multiple refactors for readability and consistency