_List of Desired Features_

Categories work based on selection, not just highlight
 - i.e. assign categories to multiple books at once
 - this may involve extra logic if books don't have the same categories beforehand
Regex Search
Choose shown columns in browser
Support for multiple copies
 - (better support, that is)
Search function in db_layer
 - eventually something which takes things like "title:foo author:bar some other keywords"


_Code Quality Improvements_
Make the various windows centre themselves
Document all functions
Conform to python naming conventions and code style
Make db_layer use a helper function to handle most of the database queries
Unify the db_layer interface w.r.t. whether book_ids should be passed as
strings or ints or dicts.


_Bugs_
Error when entering bad ISBN e.g. 02010798X (instead of 020107981X)
 - seems to be an intermittant error, likely related to polling openLibrary
Error on search 
 - related to strings in Python3
When the top element shown is highlighted in the browser window, and pgUp is pressed (causing a scrollup), the bottom border of the window turns into 'qqqqqqqq'.
 - does not happen when up_arrow is pressed.
Error checking out an already checked out book
 - SQLite integrity check failure



_Implemented Features_
Sort by column in browser
Support UTF-8 for everything
Search ignores Case (for lowercase search strings)
Text entry supports longer string
Home and End navigate to top and bottom of catalogue respectively.

Support for multiple copies
 - books will have their book_id written in pencil on inside cover