Begin to redevelop console content buffers to simplify them and allowing to have many consoles pointing to the same buffer
Separate wxTerminalParser in a separated couple of files and rename it in TerminalParser as it is not wx-dependant.
Add doc and move some function to clarify code.
Remove wxTerminalContent as it is not used anymore (replaced by simpler wxConsoleContent).
Better caret handling.
Declare and use a default invisible character in content buffers.
Fix scrolling and caret position problems.

Derive from wxWindow instead of wxScrolledCanvas
Store the console position in historic (instead of basing it on window scroll position)
Simplify scroll and caret position computation
Begin of erasing (wxTerminalCtrl::onED) implementation
Add traces for testing