Fix #140 and #139 by adding an Inward/Outward mechanism for remote call

[jeromevalentin]

#140 : The priority between error / result is now the same between TCP / HTTP. If an error and a message is returned, the error is now considered (in both TCP/HTTP) as more important and the act call fail.

#139 : An implementation for the server side is proposed. It allows to define an inward/outward hook in listen options. Those hooks are automatically invoked when receiving a remote act call.

• Inward implementations can alter the incoming message, or even reject it
• Outward implementations can alter the outgoing result, or even consume an error and produce a default response

Examples:

• Inward mechanism can be used to improve security checks, by extracting the user token from the request, ensure user is known and logged in
• Outward mechanism can be used to clean up response before they are sent, like removing all $ properties in case of seneca-entity usage on server and not on client

[coveralls]

Coverage increased (+1.1%) to 85.714% when pulling 27fa44c on jeromevalentin:inward-outward into 6b163bb on senecajs:master.

[coveralls]

Coverage increased (+1.1%) to 85.714% when pulling 8097ba7 on jeromevalentin:inward-outward into 6b163bb on senecajs:master.

[coveralls]

Coverage increased (+1.9%) to 86.447% when pulling 2a1f310 on jeromevalentin:inward-outward into 6b163bb on senecajs:master.