dynamic resizing: updates and code refact

1. Following many suggests, now the brush tool pointer is iconic
2. Sizeable tool cursors can change from icon to visual guides (circles) when resizing them dynamically. Circular cursor drawing code was implemented in basetool.cpp. I thought it was the best place but polyline isn't accepting the new feature so it's resizing the old way.
3. Code refact with a small optimization.