#1194 Add clustering parameter options to multi-level splitter

Changes:

• Enum and boolean options are extended with a function to convert an option value back to text.
• Applied that new function to a few other options.
• Moved clustering default parameter settings to constants in ClusterInput
• Clustering options use the ClusterInput constants as their default value and construct their option text from them.
• Adapted the hard-coded default clustering option values as default, since those were user-facing.
• Adapted the expected output to compensate for the modified default clustering values.
• Added the clustering options to the multilevel application, and injected their value into the clustering step.
• Added a test that requests (and gets) a bus in multilevel tests.

The following are end-user visible:

• Clustering options for multi-level splitter.
• For the multi-level splitter, the default evaporation changed from 2.5 to 2.0, and the default inflation changed from 2.5 to 2.0.

Closes #1194 (closed)