So it will be recognized by gitlab

- Remove the very host specific configuration from config/__init__.py
  and replace it by generic default values (no URL specific themes;
  'fsi_inf' as default theme)

- Add documentation for the two variables 'default_theme' and
  'themes_by_url' so that site admins can overwrite them in their local
  config.

will create stacktraces if not set

Gentoo, for example, installs it as "pdf2txt.py"

this is the preferred solution to avoid hardcoded hostname-urls and breaking
alternative port-numbers

fixes #235

Define default values in global config and allow to overwrite them in
site config.

fixes #240

Fixes#16

Prevents the sending of any mails if set to False

fixes #233

closes #236

Used as "From" header for all outgoing mail