Refactor server to allow multiple projects to be launched

Big refactor to split the actual document management of the live editor from the flask server class. This will allow multiple documents to be edited by the same server.

• Split live editor class code from the server class
• Create new class for managing live server
• Modify functions that interact with local file system not assume they are in the working directory
• Add back end functionality for launching multiple live editors
• Add vue interface for launching editors
  • Open existing projects
  • Create New projects
  • Get title correctly for projects
  • Remove project cards
  • Save changes to project list for future sessions
• Tidy up TODOs in code
• Add docstrings