* Add possibility to add hidden posts with PostCreator
* FEATURE: Create hidden posts for received spam emails
Spamchecker usually have 3 results: HAM, SPAM and PROBABLY_SPAM
SPAM gets usually directly rejected and needs no further handling.
HAM is good message and usually gets passed unmodified.
PROBABLY_SPAM gets an additional header to allow further processing.
This change addes processing capabilities for such headers and marks
new posts created as hidden when received via email.
