This refactoring allows the user to use the "enter" key to go to the
next field to fill while create a new user

This refactoring construct manually the UI to add new user groups to
allow the binding of the 'enter' key to the validation function.

This is typical for empty databases.

The transformations are applied from the end of the array. Putting the
scaling factor before the translation for the ruler_offset make the 0,0
point of the ruler stable on scale change (otherwise, the 0,0 point
being moved by the ruler_offset value, it's position change on scale change)

Since the image is streched in the svg, we need to take into account
this ratio in the resolution calculation.

The blur was created because the original svg ruler was too small. This
patch increas the base size of the image by a factor of 10, and reduce
the displayed size accordingly.

This event is also recognized by Firefox

This patch should produce the same result on Chrome but fix the display
on Firefox.

This commit change the design of the ruler and place all the elements in
a svg g element. This allows to use transforms instead of calculating
all the x,y coordinates of all staring and ending points of every line