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 27fa44c3b4bbbcf16f88eda49d46976c3691e3c4 on jeromevalentin:inward-outward into 6b163bb5bb0d31b47be1ce8ddea5d360d24e3846 on senecajs:master.

[coveralls]

Coverage increased (+1.1%) to 85.714% when pulling 8097ba7a49f6e5df26b1a5d51fcb62ba7088aa27 on jeromevalentin:inward-outward into 6b163bb5bb0d31b47be1ce8ddea5d360d24e3846 on senecajs:master.

[coveralls]

Coverage increased (+1.9%) to 86.447% when pulling 2a1f3109e323595d054e93426ce6bc19cf9d266e on jeromevalentin:inward-outward into 6b163bb5bb0d31b47be1ce8ddea5d360d24e3846 on senecajs:master.