DXF qiewer

A simple viewer for 2D-DXF files.

Files are opened in the Explorer, thus read from the SD Card.
No editing possible in any way, can't save DXF files -> no permissions required.

Controlled by:
- 1-touch: move / select point
- 2-touch: zoom / rotate
- 3-touch: fit to screen

Supports these elements:
* POINT
* LINE
* ARC
* CIRCLE
* TEXT
* LWPOLYLINE
* SPLINE
* BLOCK
* ENDBLK
* INSERT
* DIMENSION
* SOLID
* ELLIPSE
* POLYLINE
* VERTEX
* SEQEND
* MTEXT