Print blobs reduction

Printing with latest versions was causing blobs during prints:
![before](https://cloud.githubusercontent.com/assets/5079803/3508842/2400d574-0691-11e4-9239-f1d82ddcb17c.png)

To reduce them it was inserted a clipping algorithm in the writeGCode method to clip points for a limit distance (new SETTING). Depending if it is a INNER or OUTER wall a retraction or a fast move is done.
After results show improvements:

![after](https://cloud.githubusercontent.com/assets/5079803/3508871/955c6562-0691-11e4-951e-04b15d93b2ef.png)

Algorithm behavior:

Planner (previous)

![cura_3](https://cloud.githubusercontent.com/assets/5079803/3508899/28a89dfe-0692-11e4-9b5f-865e83f6e68a.png)
![cura_4](https://cloud.githubusercontent.com/assets/5079803/3508900/2bdb3c20-0692-11e4-87d6-3d5afaf5b83a.png)

Planner (after)

![cura_13_5](https://cloud.githubusercontent.com/assets/5079803/3508906/46c3b274-0692-11e4-900a-0a3a6c88ff95.png)

Clipping with retractions (after)

![cura_13_3](https://cloud.githubusercontent.com/assets/5079803/3508927/acf8db82-0692-11e4-8e63-d8a9b4157dd4.png)

![cura_13_4](https://cloud.githubusercontent.com/assets/5079803/3508929/afe1e816-0692-11e4-8e4f-5986f0602ccf.png)


Summary:

* New setting - pointsClipDistance  (settings.cpp)
* New GCode path configuration data constructor -  void setData(int speed, int lineWidth, int clip, const char* name)   (gcodeExport.h)
* New GCode export algorithm when clipping and spiralize is off (gcodeExport.cpp)
* GCodePathConfig (inset0Config and insetXConfig) using setData constructor to support clip  (fffProcessor.h)
* New GCode moves for Inner and Outer walls with clip, if not spiralize.