Releases for PDFPreview

Changes since 8.x-1.0-rc1:

Issue #1532146 by iantresman: remove generated image
Issue #1538354 by iantresman: nicer filenames
Issue #1286782 by r.aubin: filenames with spaces (and other non ascii7 characters also)

Some code backported from 7.x release, now, you can manage the quality of extracted previews.

This release has a lot of changes to adapt it to new features of Drupal core.
Some settings has been moved from module settings to field instance settings, so, you can have several fields showing previews of pdf files on differents manners, and this gives the formatter much more power if you use it on views.
Now you can select which image style to use, instead of fixed size from 7.x-1.x release.
Some code has been suppressed in favour of image module, and some in favour of file module, in order to keep this code as small as possible, and potentially reducing bugs.

First development release