QuadricT: implement Q+Q and Q*scalar operators for convenience.

See merge request !113

Doc Build

Automatically build the documentation again

See merge request !112

Feature mesh conversion

implements a cast from polyMesh to Mesh and vice versa using  static_cast<Mesh>(polymeshInstance) or static_cast<PolyMesh>(trimeshInstance)
as mentioned in #23 .

Copy constructors for respective mesh types were added as well as a function to copy all properties from one mesh to another.
Unittest for mesh conversions were added checking the number of vertices / faces as well as custom double vertex properties and edge properties.

Note: The used triangulation only works for convex polygons, it should be replaced by the earclipping triangulation mentioned in #33

See merge request !110

closes #23

Fixed OMWriter when no faces are available (Thanks to Jamie Kydd for the patch)

See merge request !111

Merge branch 'master' of https://www.graphics.rwth-aachen.de:9000/OpenMesh/OpenMesh into featureMeshConversion

custom properties and vertices / faces are tested

added explicit copy constructors for PolyMeshT and TrimeshT to enable static_casts of different mesh types

size_t int warning

See merge request !109

update logo file in docs with new font weight

See merge request !108

attempt to quench 'Checked Iterator' warnings in VS2015

See merge request !107

Warnings ok

See merge request !105