Quickview changes:
1) Close the quickview window on library change. Keeping track of what should be shown in the new library wasn't working.
2) Add keyboard shortcuts to move between quickview's controls.
3) Add a checkbox to "lock" quickview's contents, preventing their change when moving around on the main spreadsheet.
Merge branch 'master' of https://github.com/cbhaley/calibre

Quickview: Add a checkbox to lock the quickview window so that it does
not change while moving around in the main book list

Quickview: Auto-close the quickview window when changing libraries