Fix cross-references in the manual.
Remove binding for `N' from ebib-index-mode-map.
View file: use file from cross-referenced entry, if present.
Fix previous commit.
Fix previous commit some more
Add `ebib-key-regexp' and update `ebib-bibtex-identifier'
Report an error when an illegal identifier is found.
Manual update.

Add a warning about possibility of losing entries when errors/warnings are
found in the .bib file.
Add line numbers to illegal identifier errors.