install files changes
changed behaviour of expansion / collapse of extr.point

* new ext.points are created in a distance with respect to the current zoom level, or if available the dist to the parent point
* contour sacles up a bit if new children are created, scales down if deleted
fixes #37
cont-points detetion radius is now scale dependend. cpoints only get deleted if a cpoint is moved

one can now pass over an ext.point over an other without loosing c.points
fixes #36
started crosshair
crosshair working
color crosshair
finished fast rulers
better ruler
made ext.points smaller, but bigger catch area around
made cpoints visually smaller, but catch area bigger
ruler2 bugfix
nothing
ui overhaul > svg

* smaller points, visually, but the (invisible) active region where you actually can click is bigger.
* aim-mode: when moving a extremal point, most of the spaghetti is hidden and a cross-hair is drawn for better aiming.
* fast ruler mode: the ruler now behaves totally different: click and hold: one appears, drag: change size, let button go: disappears again.
* expanding / converting one extremal point to saddle and 2 others is more intelligent now (increases spaghetti, takes general orientation
and zoom level into account, no more need to zoom out and in again)
* and some bugs fixed (contour points don't randomly disappear)
fixes #37, #36