WebStyle: use utf8 for jinja2 str to unicode

* Jinja2 requires all strings to be unicode. Invenio however operates with
  UTF8 encoded 8-bit strings. Jinja2 will automatically convert non-unicode
  objects into unicode objects, but using ASCII codec. This function
  replaces the escape function and Markup class in Jinja2, to use
  UTF8 codec instead when converting str objects into unicode objects.

Co-authored-by: Jiri Kuncar <jiri.kuncar@cern.ch>
WebStyle: werkzeug debugger for devel sites

* Enabled Werkzeug debugger if CFG_DEVEL_SITE is greater than 8,
  independently of if an application is running in Apache or in
  a development server.