Implement project saving/reloading, proper application state tracking

[ghost]

Currently, new projects are created automatically based on their trace contents. Generated data files are kept around forever, until the user manually deletes them.

The user should be able to save and reload projects. The "current opened" project should store its state (database files, etc.) somewhere, and upon saving the project that state could be moved to the requested location. If the project is discarded, then the data files should be cleaned up.