Add additional configuration options to the UI

[jon-axon]

The Chipolata emulator library allows persistence of options sets to disk and easy re-loading, however there are also elements of the UI itself that can and should be configurable but currently are not. For example:

• The range of the CPU cycle/s (target) slider is hardcoded to 100-10,000 hz
• The foreground and background colours can be configured at runtime but cannot be saved; they always revert to defaults open re-loading the Chipolata exe
• The keymap is hardcoded into the binary code (and as such is probably unusable on anything but a QWERTY keyboard)

So, the UI should be enhanced to provide a mechanism for the above to all be configured and persisted to disk, with user-defined default values then loaded automatically along with Chipolata.