Added more display options to handle more types of content

[robspearman]

I have a need for users to share their own images and files and this plugin was very close to what was needed. Rather than make a fork, I added my changes as options so that anyone can decide what combination of features they want. I hope that these will be welcome additions, although I am completely new to Ruby on Rails and there may be some issues!

Changes:

• Optionally show thumbnails on lists (the first attachment with a valid thumbnail is used)
• Optionally render attachments before the content section of articles (useful when files are more important than the content field)
• Option to have one large article page rather than using tabs (usability)
• Option for article breadcrumbs on index lists (usability)
• Category icons can be created using CSS for index page
• Show article summaries on lists if summaries are enabled
• Added rating and author columns to category lists
• Prevent tags with spaces from splitting across lines and make more legible
• Added "Unrated" label for articles with no votes
• Show existing attachments on article edit page
• Search summary field (important for users who use this field)

I have also fixed a number of the outstanding issues for the project.

Known issues:

• I did not spend much time on CSS beautification. Layout could be improved.
• I added English translations for new labels, but wasn't sure if more was required for other languages other than getting translations.

[archonwang]

Wow， it seems great, anyone has tested it on redmine 3.3? Thanks.