Add the ability to add a run as a subsplit using Markdown syntax.

[TanookiMario65537]

During multi-game runs, it would be nice to compare to PB, golds, or other comparisons for the run currently in progress. If the runs are just specified using the syntax (run name)[path to .pysplit], we can load the data for the sub-run along with all its comparisons and have the ability to show those comparisons. We can also save the run that takes place during the multi-run as a run in the sub-run once we're done.

[TanookiMario65537]

This is all in the first commit on the associated branch, but I think an issue is a more appropriate place for this information because I can add to it without having to rebase everything.

• Need to be able to load the splits for all the referenced runs. This
  includes:
  a. Actually loading all the split data.
  b. Adjust the split names by removing run-defined groups and instead
  having a super-group with the name defined by this run. Will also need to deal with re-indexing bot counts here.
  c. Building the list of split names from the loaded runs.
• Need to be able to save the splits for all the referenced runs. This
  includes:
  a. Searching the current run for each of the sub-runs and adjusting
  the total times.
  b. Updating golds for each sub-run.
  c. Saving the start and end times for each run during the run. This
  will need to happen during split ends and partial saves as well.
• Need to create comparisons for all the referenced runs. This
  includes:
  a. Adding/removing comparisons when a run is started/ended.
  b. (Maybe) saving the comparison number if we end a run showing a
  sub-run comparison. We should add a new comparison type for sub-runs
  as well to allow for this.
  c. Prepending the appropriate number of splits for a sub-run
  comparison with blanks (or maybe match the current run instead?
  I haven't decided on that yet).
• Need to figure out a way to make sure that when a sub-run updates,
  the runs that use it also update.
• (Likely also necessary) Get rid of direct references to the save data dictionary from outside the state class.