Calculate relative paths for all files.

This fails for some diagnostics paths, but it may
be possible to work out what they meant and transform
them back!
Minor commenting improvements.
Consolidate index_opi_paths and index_paths into one function.
Search scripts for paths references to re-index.
Remove opi.dir macros from EDM launcher file.
More accurate recursive indexing.
Warn if there's a clash in recursive dict update.
Rename path to directory in index_dir.
Unit tests for update_paths.
Make index_dir a bit more understandable.
Use library functions to manage paths.
Update macros and versions in launcher opi.
Remove reference to my home directory.

Tidy and comment spoof_edm function.
Tidy calculation of 'depth' of opi file.

Improve variable names and comments.
More descriptive variable names.

opi_index and path_index instead of opi_dict and path_dict.
Rename update_paths.py to paths.py.
Make methods and functions private where appropriate.

Change paths.parse() to paths.update_opi_file().
Merge branch 'no_paths'