MaterialCard improvements

• Neẃ improved MaterialCard shown in the overview page, broken down into four sections:

  • Composition: formula, elements, material name, etc. Always shown.
  • Symmetry: all symmetry related properties. Shown only if symmetry data is available (bulk materials), otherwise showing NoData.
  • Lattice parameters: Lattice parameters for the currently selected structure. Shown only if data is available (materials with atomic structure and unit cell present), otherwise showing NoData.
  • Structure: Shows the 3D viewer for the currently selected structure. Shown only if data is available (materials with atomic structure), otherwise showing NoData.

  This layout should accommodate all types of data: simulations with/without symmetry or lattices and experimental data which typically has only composition. If there are any structures present, there is a dropdown selector in the top right corner for selecting which one is shown (affects Structure and Lattice parameters).

• Improved and extended tests: I created proper tests for MaterialCard and greatly simplified the GUI test setup and usage in general.

• Added angles as a new unit in the GUI (needed by angles used in lattice parameters).

• Homogenized the look of tables containing data from metainfo (e.g. Symmmetry/Composition/LatticeConstants are now shown within a table, bulk/shear modulus and band gaps are shown within a table. The new look adds thin borders around the tables to make it easier to recognize where the contents start/end. This was especially a problem in the new MaterialCard where without the borders the different sections are harder to distinguish.

@mscheidg: I'm open to any suggestions for modifying the new look. I can make the changes before merging.