Add possibility to install several (FEniCS) branches side by side for Dorsal

Add lightweight support for: - Installing different branches than stable and trunk (for instance 1.0.x or 1.1.x) - Installing several branches side by side in a consistent manner.

Support dorsal driven installation for dolfin-olm for DOLFIN-OLM

It should be fairly easy to add dolfin-olm support to dorsal. It basically needs package files for dolfin-olm and gts, where the gts one should include a patch as well.

Implement sliding meshes for parabolic test case for DOLFIN-OLM

As a first testcase for the sliding mesh method i 3D, finish and test the 3D testcase prepared in demo section. Test 3 version with cylindrical convection, with arbitrary convection and without.