adding header files to targets as suggested by brian

Common/CMakeLists.txt

Fltk/CMakeLists.txt

Geo/CMakeLists.txt

Graphics/CMakeLists.txt

Mesh/CMakeLists.txt

Numeric/CMakeLists.txt

Parser/CMakeLists.txt

Plugin/CMakeLists.txt

Post/CMakeLists.txt

Qt/CMakeLists.txt

Solver/CMakeLists.txt