Settings for plugins how to treat content (nl2br, truncate and more)

More control over formatting the plugins content.

- In Plugins settings for each plugin added "Treat with options
"As is", "nl2br (from text only)", "strip_tags (from html)", "strip_tags but img,a",
and Truncate (0 means not to display content for this plugin).

Then it is implemented in the html templates. For this purpose a modifier is created: nlTreatContent.

Related to #90.