Add another class of plugins: tools about meshlabjs HOT 1 OPEN

The main idea is that at certain event the js part invokes a cpp function that perform the "hard" part of the task (like for example selecting or reporting the info about the clicked point).

For this task we need a consistent way to pass the viewing information between the js system and the cpp part. This is fundamental because the processing part is done with actions defined in screen space.

For example this is what happens when the info picking tools is started:

• the icon of the tool is enhanced and in the tab below the option of the tools appears
• the icon of the mouse is changed and the selected tools grab the mouse focus. Since the activation of the tools all the mouse events are intercepted are intercepted and managed by the tools. Pressing alt allow to bypass the tool and the mouse event are passed as usual (so mouse movements rotate the object)
• when the user do a mouse down mouse up release, the framework call an 'apply' method of the tool plugin with the current camera parameters and the mouse position.
• camera parameters are passed using a vcg::Shotf object

from meshlabjs.