Internally it was only invoke callback set for an
operator template. This invoke was setting such
properties as mouse_x and mouse_y and was calling
an exec function.
This meant that t seemed to be really easy to
use node.select operator from by giving a mouse
positions, but in fact it wasn't possible (because
it requires exec callback)
This commit sets operator's template exec callback,
which makes it possible using node.select from
python.
Sergey Sharybin
791be2f79f