Export BEM++ so it is available to other cmake projects

- Exports both build directory (if NOEXPORT not defined) and install
- Headers copied to location in build directory so BEM++ can be included from install or build
- Example/test project in tests. Checks compilation + linking the dirichlet tutorial using a CMake
projects that uses the export of the build directory.

- Issues
   - [x] Closes #81
   - [x] Closes #77
Remove unnecessary cmake option in setup.py
Merge branch 'rsdt/new_build' of github.com:bempp/bempp into rsdt/new_build

Conflicts:
	setup.py
:lipstick: removed trailing whitespace
Moving patch files to subdirectory in cmake
Sprucing up test project

- More verbosity
- Tests for bempp target
- Deletes directory prior to running test