Improved metadata support

Changes in tapeimgr 0.4.0 (relative to version 0.3.0):

• Tapeimgr now writes a metadata file in JSON format
• Both GUI and CLI support entry of basic descriptive metadata (identifier, description string and notes).
• New defaultDir variable in the configuration file allows one to set the path that is opened after pressing Select Output Directory (by default the user's home directory is used).

Note on upgrading from previous versions

If you installed an earlier version of tapeimgr, you will need to generate a new configuration file (configuration files from older versions will result in an error message). This can be done by simply running the tapeimgr-config after installation. For a global install the steps are:

1. Upgrade tapeimgr:

    sudo pip3 install --upgrade tapeimgr
   

2. Configure the new version:

    sudo tapeimgr-config
   

And for a user install:

1. Upgrade tapeimgr:

    pip3 install --user --upgrade tapeimgr
   

2. Configure the new version:

    tapeimgr-config
   

Done!