Minor fixes
Moved common static page functionality into an abstract page.

Fixes bug 2827.
Reordered fields, no functional change.
Provide default value for possible backwards migrations.
Removed unneeded check.

We can safely assume Django is > 1.3
Split except clause for handling different exceptions
Move check for accepted markup filter names to get_markup_filter_name()
Add get_markup_filter()

Now get_markup_filter_name() only returns a nice version of the filter name
for showing on the UI.
Fall back to HTML markup when markup configured module is missing

This fixes bug #2380.
spelling fix
update from wiki, remove obsolete ref, link to translate docs
use code-block:: bash, non-inline hyperlink targets