Support FSI with fenics as a Structure Solver

[richahert]

Enable the adapter to be used for FSI with FEniCS as 2D structure solver.

List of new features:

• Introduce treatment of vector valued data and functions in FEniCS. Displacements and Forces are vector valued functions and have to be treated correspondingly.
• Buffer the RBF interpolation in the CustomExpression class for runtime improvement in FSI simulations
• Use PointSource for quantities that are mapped conservatively and are applied to mesh nodes (used for Forces)
• read_block_vector_data and read_block_scalar_data are wrapped into read_block_data that differentiates between the two cases (scalar/vector) and calls the respective preCICE function

Open ToDos

• make the 2D-3D mapping more user friendly (solved by 2c9c2a0)
• find a proper treatment for application of point Forces
• fix automated testing (see Support FSI with fenics as a Structure Solver #38 (comment))

[BenjaminRodenberg]

I created a branch richahert-fsi-pr on this repository, since I do not have the rights to push to richahert:fsi-pr (for details on how to fix this, see here). As soon as I have the right to push the changes. I can move everything to this PR.

[BenjaminRodenberg]

I created a branch richahert-fsi-pr on this repository, since I do not have the rights to push to richahert:fsi-pr (for details on how to fix this, see here). As soon as I have the right to push the changes. I can move everything to this PR.

I was able to merge the branch. I was actually using the wrong remote URL. See https://coderwall.com/p/7begkw/fatal-remote-error-you-can-t-push-to-git

[BenjaminRodenberg]

@shkodm Currently, the tests are not working. Probably something with the FEniCS installation on Travis is wrong.

[BenjaminRodenberg]

I ran the current version of the adapter with the flap test case from precice/tutorials#38. As soon as the automated test are working, we can merge this PR.