* get rid of BlockReturnType: it was not needed, and code was not always using it consistently anyway
* add topRows(), leftCols(), bottomRows(), rightCols()
* add corners unit-test covering all of that
* adapt docs, expand "porting from eigen 2 to 3"
* adapt Eigen2Support
I think that because MatrixFunctions is in unsupported/ and MatrixBase is
not, doxygen does not include the MatrixBase methods defined and documented
in the MatrixFunctions module with the other MatrixBase methods. This is a
kludge, but at least the documentation is not lost.
The latter is more stable. This fixes one of the issues with the test.
Also, make typedef's in MatrixFunctionReturnValue public; this is
necessary to get the test to compile.
This does the job but it is only a first version. Further plans:
improved docs, more tests, improve code by refactoring, add convenience
functions for sine, cosine, sinh, cosh, and (eventually) add the matrix
logarithm.