feat - verbosity level

i propose adding a new concept of VerbosityLevel

this would correspond to a integer from 0 - 10, added to Session

• 0 corresponds to the default, it means a skill should speak only essential messages
• 10 corresponds to the skill speaking a lot, ideally explaining everything it is doing along the way

a skill would check for self.verbosity_level (session aware) and conditionally speak more messages, backwards compat is retained

if self.verbosity_level > 3:
    self.speak("extra info")
if self.verbosity_level >= 9:
    self.speak("extra very redundant info")

using session allows verbosity level to be set per client (such as hivemind voice satellites), the default value would come from mycroft.conf as usual. a companion skill can also be made to control this by voice