Added app2app support for peer mode

Changed app2app to dynamic service and added state listeners. Now the
PZP will register the app2app service only if the PZH is disconnected.

Jira issue: WP-681
Merge pull request #468 from fabianatwork/WP-681-App2App-Peer-Mode

Added app2app support for peer mode
Refactoring of Arduino folders. First implementation of Serial driver
for Arduino

Jira issue: WP-754
Merge pull request #470 from glatorre/WP-754

Refactoring of Arduino folders. First implementation of Serial driver for Arduino [WP-754]

mlasak: "what about the multiple files with same contents"

glatorre: "the serial_driver.ino file is currently the same for both the boards because the behavior is also the same. However I will enhance the mega version (rising a new jira issue) adding the capability to read sensors/actuators information from the SD card."