Weekend Work [GITHUB]

I added:

- Repo Config Modal: so you can change the current repository and if there is a failure it pops up
- Loading Progress Bar: when initializing the workspace
- Image Uploading: the OPF and XHTML files are updated when an image is added using the Image toolbar button
- Creating new XHTML files: they were not being added to the OPF files which caused errors
- Moved `META-INF/container.xml` into a separate Model: this is to support adding new books