new instant eraser, wysiwyg tool adjust. improvement and tools reset

1. Now, CTRL+SHIFT applies brush size to the eraser and temporarily
selects it.
2. "wysiwyg" tool adjustment is now more precise.
3. tool reset added to menu/tools. Prevents from persistent crashes
caused by corrupted settings file .
Resolve #26 , Tool cursor(pencil tool) now displayed correctly when program start.
Resolve conflict