restore:
DONE group titles by first letter
DONE summaries for libraryTrees
DONE progress indicator in library activity
DONE book search
DONE books for series _and_ author
DONE update book collection on path changing (from options dialog)

new:
DONE filesystem event listener
DONE read book => go to library => go to book info => update book info => return to reading mode: book info is not updated
DONE 'rescan' button in library menu
DELAYED getHelpFile => getHelpBook
DELAYED move BookCollection to libraryService package; change access rights to package local

bugs:
* trim author names in fb2 (and may be in other formats)
DONE action hyperlinks
* double tap only for action bar
* text search => found multiple occurencies => turn page right => right button is disabled

small features:
* min/max font size
* decrease min brightness level

large features:
* two page view
* bookmarks highlighting
* https://en.wikipedia.org/wiki/Alphabetical_order

plugin:
* bookmarks import/export
