refactor setup function

[soundanalogous]

• split wifi init and firmata init into separate functions
• add hostConnectionCallback

[soundanalogous]

TODO:

• Report connected or reconnected state to host
• Report current state or any missed changes to host (per provide a query to report pin values in bulk protocol#59), only on reconnect
• start / restart sequence counter?

[jnsbyr]

A change to the systemResetCallback() is required for the ESP8266, at least when SERIAL_DEBUG is enabled. A possible solution is described here.

[jnsbyr]

To prepare the usage of the hostConnectionCallback for the other host connection types where the transport layer is not connection oriented (serial, BLE serial) the watchog timer must be placed in a method that is periodically called (e.g. maintain). A possible solution is to insert a class inheritance level between Stream and all currently used connection type specific stream implementations, maybe calling it FirmataSteam. This class could handle

• connect/reconnect distinction
• watchdog mode (disabled, send only, send and receive)
• watchdog sequence, telegram transmission and receive telegram monitoring
• calling the hostConnectionCallback for non connection oriented streams
• closing the connection oriented streams on watchdog timeout

[soundanalogous]

Going to merge this and defer any additional changes regarding hostConnectionCallback to a future PR after the protocol definitions for watchdog and connect/reconnect have been finalized.