Joystick to keyboard mapping and secondary BBC joystick support

Assigning host joystick axes and buttons to BBC keyboard (up to 4 joysticks or gamepads separately).
New human readable file format for joystick to keyboard mapping (see Documents/JoystickMap.txt)
Changed joystick API from WinMM to DirectInput
Display joystick names in menu
Option to automatically load image-specific joystick mapping file (same as disk name, but with .jmap extension)
Added "unassign" to keyboard and joystick mapping dialog
Highlight assigned keys in joystick mapping dialog
Added second BBC joystick support
Select PC joystick and axes for each BBC joystick
Save joystick order in preferences file
Added "Change Joystick Order" dialog
Added Joystick Sensitivity parameter
Change Digital Mousestick handling
Map additional joystick buttons to analogue port PB0 and PB1
Removed "Basic Hardware Only" option
Unmute when keyboard mapping dialog is closed
Separate fire buttons on BBC joystick

Another redo of PR #87. Rebased branch because previous one became messy.

stardot / beebem-windows