Option for ignoring BDFM1 mass lumping

In the BDFM1 lumped mass matrix an additional option allows the user to ignore the mass lumping, i.e. in this class the full matrix will be used for multiplications and divisions.
Refactoring of lumped mass classes

Created a common base class for LumpedMassRT1 and LumpedMassBDFM1 and added a test which compares the kinetic energy for a solid body rotation field as calculated with the full= and lumped mass matrix to the exact value (4/3*pi).
Bug fix related to lumped mass matrix refactoring.

The internal name of the lumped mass matrix changed.
Important bugfix in lumped mass matrix.

For the diagonal case, the lumped mass matrix was calculated incorrectly
Added kinetic energy test for lumped mass matrix.

Calculate the kinetic energy both with the full- and the lumped mass matrix.
Improved output for kinetic energy test of lumped mass matrix.

Print the error (i.e. relative deviation from exact solution) as well as the absolute value of the kinetic energy integral.