security: shellwords escape attachment file names to prevent remote code injection

Merge peristent temp files and fix quotation of shellwords escaped string

s|returnded|returned|

Conflicts:
	doc/Hooks.txt
	lib/sup/message_chunks.rb
security: prevent remote command injection in content_type
security: link to wiki page on view-attachments
Bump to version 0.13.2.1

Conflicts:
	lib/sup/version.rb