Use proper "document-viewer" directory for viewer

Also add a bit more documentation on scripts usage
Use "x_documents" vs "document" for i18n plurals

There were several places where the templates incorrectly
used "document" as a plural form.  The x_document is more idiomatic
for that.  This removes the plural "document" string and replaces
it's usage with "x_documents"
Brighten contrasting shared document count color

Was a very dark gray on black background, basically unreadable.