Create Mailhandler analyzer

Problem/Motivation

Inmail has a concpet of analyzer plugins. Its main purpose is to analyse the mail message and they are executed before handlers.

Proposed resolution

Add MailhandlerAnalyzer that should provide 2 methods: findSender() and findUser(). As a part of this issue we should create MailhandlerAnalyzerResult and add sender/user to the result. Later on, in MailhandlerNode we will use the MailhandlerAnalyzerResult to find out if user is authenticated.