Added IPTC parsing by pyExiv2 module

[yozkiyokly]

For photographers who taging theis collections using IPTC metadata. IPTC is much flexible than EXIF because IPTC supports more descriptive text fields (EXIF have only one - "comment" field). In this release IPTC "title" field have a little priority over EXIF "comment: field. Part of this logic implemented inside exifread code block. Added module pyExiv2 linkage with several checks.
If user have no pyexiv2 installed, nothing happens.

I leave several huge comments blocks inside code. This is my first python release, so excuse me please for unclean code. It works, it parses. Three days of work and it is here.