Improving speed of index notation

[jstoobysmith]

When building HepLean there are couple of files which take a very long time to build, and I think contribute significantly to the overall build time of the project.

I believe that these slow files are all related to Index notation and depend on files within ./HepLean/Tensors.

Below are the tasks related to this issue:

• Identify the modules (files) within HepLean which take the longest to run.
• Identify the specific reason why these files take a long time to run (most likely this is something to do with elaboration of index notation).
• Improve the build time of these files.