add Gauss quadrature on triangles
add FeTRI3
add tests for FeTRI3
fix compiling errors in MSVC
Merge pull request #403 from norihiro-w/fix-fe_errors

fix compiling errors in MSVC
Merge pull request #388 from norihiro-w/add-fe-tri

Add FE type TRI3
Small fix for the ninja build system.

See http://docs.opengeosys.org/docs/devguide/advanced/build-with-ninja