[Inkscape-user] Meassure improvements, Speed and Phantom mode

Hi to all. A just commit a new feature in meassure tool, allowing compare two measures, creating greyed version of current meassure in a temporary way.

Based in a comment on original code I could improve the response of the tool.

Also want to make numeric inputs for start and end point, thinking add it as a modifier for the knots instead puting them on the toolbar.

Here a video: http://jabiertxof.marker.es/2016/02/meassure-tool-phantom -and-speed.html

Cheers, Jabier.