Idler for Schlot bowden extruder

The idler is based on Schlot idler "http://www.thingiverse.com/thing:275593"

Designed a bearing adapter to be able to use back the Sunhokey stock extruder bearing.
Idler change to mounting using M4 screw. (Required tapped m4 thread on the hole)
Included some M4 spacer for position adjustment and for different screw length.