Cosmetic
Fix Invalid token path "R, e, f, e, r, e, r". Valid paths are: Referer #3536
* Adding a more generic vulnerability assertion method
* Adding feature to run all plugins of a class in the PluginTest
Fix Header value must be a string." at headers.py:__setitem__():114 #3535
Fixing serialization issue found while scanning demo.testfire.net
Cosmetic
Less (useless) calls to dc_from_hdrs_post