Upgrade to FEniCS 2019.1.0

[Tormod Landet]

The 2019.1.0 release of FEniCS is scheduled for February 22. 2019

There are no expected problems due to the upgrade, but the following tasks have to be performed:

1. Update Docker and Singularity images and test Ocellaris on these
2. Push image to DockerHub and switch the CircleCI config to use the new images

After upgrading, the following should be fixed

1. Take advantage of some of the updates to DOLFIN, see e.g. DOLFIN pr 511 which can replace some of the code in meshio.py
2. ...

[Tormod Landet]

FEniCS 2019.1.0 has now been released. I hope to look into this issue within a month

https://fenicsproject.org/docs/dolfin/2019.1.0/python/ChangeLog.html