Minor enhancement to fingerprint the web server operating system and

the web application technology by parsing also HTTP response Server
header.
Refactor libraries and plugins that parses XML to fingerprint and show
on standard output the information.
Updated changelog.

lib/core/option.py

@@ -454,6 +454,7 @@ def __setKnowledgeBaseAttributes():
     kb.dbmsDetected   = False
     kb.dbmsVersion    = None
     kb.bannerFp       = {}
+    kb.headersCount   = 0
     kb.headersFp      = {}
     kb.htmlFp         = []
     kb.injParameter   = None