add guides for points placement

[jimy-byerley]

At the moment, placing and moving points and directions only writes raw coordinates in the script, which usually ask the user to correct the values in order to get exact positions.This is slowing down the drawingand hard to read once done.
This issue is to rework this so that the placement can be guided (with being attracted to special positions, grid/directions) and the written value cleverly interpreter in term of the special positions and directions. This must be a mode to enable/disable

• enable/disable from toolbar and shortcuts
• there should be a way to select the active special directions (could be any vector, axis or matrix, not only x,y,z in the view)
• when attracted to a special position, the placed point position must highlight the directions or primitives it is matching
• the value written in the script must be an expression of the selected directions or matched primitives