pelicanconf.py: Update PLUGIN_PATHS setting for pelican 3.4.0 change.

No functionality change intended.
Enable TYPOGRIFY, use 'striptags' to avoid damage from modifying title.

While at it, use striptags to make use of 'SITENAME' safe
when used in a string.
Avoid wrapping literals marked with class 'pre'.

Makes for nicer experience for things like compiler flags,
symbol names, etc., however this introduces the risk
of making very long literals unreadable on smaller screens
due to overflow.  Acceptable for now.