* whisper: mailserver test introduced, refactoring
* whisper: validation test updated
* whisper: max number of peers fixed
* whisper: verification bug fixed
* whisper: esthetic fix
* whisper: interface changed to simplify the transition to v5
* whisper: preparation for version switch
whisper: project restructured, version 5 introduced
This commits adds a draft version of the new shh v5 protocol.
The new version is not on by default, --shh still selects version 2.