Fixed childsize bug in the "ratio" aligner in eelium.gui

The childsize mode of the "ratio" aligner was broken due to the
some work being done in newly created vectors. Now the real ones
are cleared and reused as intended.
curvetool.eel fixed and improved

Toggle button to show/hide lines in the graphs.

Toggle button to enable automatic clearing of a curve before
re-rendering.

Added z axis for rendering of 2D functions.

Nicer toolbar layout.