Debugger: Split into core library and application.

- Add subfolder src/kits/debugger which contains the debugger's core
functionality and lower layers. Correspondingly add headers/private/debugger
for shared headers to be used by clients such as the Debugger application
and eventual remote_debug_server. Adjust various files to account for
differences as a result of the split and moves.
- Add libdebugger.so to minimal Jamfile.

Debugger: Implement float value editor.

FloatValueFormatter:
- Implement parsing/validation hooks.

FloatValueHandler:
- Implement GetTableCellValueEditor() to accordingly return a
(newly implemented) TableCellFloatEditor. This allows variable
value editing for float/double variables.

Debugger: Implement float value editor.

FloatValueFormatter:
- Implement parsing/validation hooks.

FloatValueHandler:
- Implement GetTableCellValueEditor() to accordingly return a
(newly implemented) TableCellFloatEditor. This allows variable
value editing for float/double variables.