Linbin Screwless Borderless Stackable Labelable V2 3mm

A Linbin without border which is stackable and has a place for a label.

Fits [Frame For Linbins](http://www.thingiverse.com/thing:99973)

Made a redesign which should improve following things:
- Made all connections symmetric to simplify assembling.
- Provide a source file with basic shapes.