Allow customization of note title from extracted annotations

Adds the following four prefs to extensions.zotfile.pdfExtraction.*:

  *  noteTitle: Custom title to be used for extracted annotations.
     Default is an empty string, which falls back to the
     `extraction.noteTitle` string built-in to ZotFile.
  *  includeDateInNote: Boolean indicating whether the date should be
     included in the note's title. Default is false. Overrides
     the `localeDateInNote` pref.
  *  noteTitleHtmlTagStart: start tag for note title. Default is `<b>`
  *  noteTitleHtmlTagEnd: end tag for note title. Default is `</b>`
Merge pull request #141 from ptgolden/customize-note-title

Allow customization of note title from extracted annotations