YAML parser code style consistency in App names and related

[apsabelhaus]

Currently, the YAML parser / builder code does not meet the informal NTRT style that we have developed. For example, "BuildTensegrityModel.cpp" is compiled into "BuildModel" which is bad because the name changes, but this is also bad since BuildTensegrityModel.cpp has a main{} function, e.g., it's an App file.

We should (a) come up with specific style guidelines about file names, particularly for App files, and (b) change the YAML parser code to match.