Package as a Sandstorm app

[ocdtrekkie]

I'd like to package XRF Books as a Sandstorm app. First for private use (mostly because of #4) but eventually for publishing to the app market.

• [x] Create a sandstorm_xrf_core which replaces xrf_core and integrates with Sandstorm
• [x] Pre-populate the database tables, create a flow for new configs
• [x] Migrate existing management panels from admin system to books
• [x] Add editing capability for existing materials
• [x] Add file upload capability for cover art
• [x] Add database import functionality for my migration purposes
• [ ] Remove Jake-specific hacks (#4) so that other people can use it
• [x] Open source the code as of "reasonably usable to not-Jake"
• [ ] Add Powerbox access to https://lccn.loc.gov for import

[ocdtrekkie]

https://github.com/ocdtrekkie/xrf_books/commit/144c998c8e3fd22b3d6384bf7bdac8520395412c detects if acp_module_page.php is local or not, so that it should work in my Sandstorm package model as well as my current separate origins model.

One big outlying issue is where covers are pulled from, both the uploaded and display pages assume exactly where they are based on my current hosting setup.

[ocdtrekkie]

https://github.com/ocdtrekkie/xrf_books/commit/5ef34bf2021a1d0ebf69243e59640980539e97d8 needs to be fixed to work that way too, and we possibly should move this functionality into the header files...