Allow developers to initialize the Rest and Socket config separately

[Dahkenangnon]

See #28 for details

To fully implement this architecture,

• The old architecture will be available but deprecated until the V5.0.0
• in V5.0.0 we will remove the deprecation, so only separated configuration will be allowed

This will allow us to adapt the package adopting exactly the philosophy of feathers js client as said @dmatuschek in the #28

Is this plan good, what do you think about it?

May we keep in place the old architecture (consisting in configuring all clients at one time) even making it possible to allow separated configuration?

Please, let me know.