Tidied up and improved echo method of report class. This much improves the presentation of the ls functions.
New experiment philosophy: experiment directories and experiment files can now co-exist in the same project directory. This removes the need for the recently introduced mode= by_file, by_dir argument. Introduced the unsqueeze function and modified the squeeze function so as to store the squeezed grid elements into the new squeezed_dims (a grid object) attribute of fields. Fields are squeezed upon loading, but unsqueezed when saved. Can now also link a project to a single file (instead of project directory) by specifying a file in the project class argment.  Some bug fixes.  Improvements around file io using try statements.