Core-488 Allow relocation of data folder outsite the application, for example in Dropbox

With this change is possible to copy and paste the freedomotic data folder into dropbox, samba share or any local or remotly mounted storage. 

USE CASE:
This allows you to edit the environment and automations using the freedomotic instance on PC, and then use the same data in a freedomotic instance on a headless Raspberry Pi.

HOW TO:
add this property in config.xml file
KEY_DATA_PATH=/home/enrico/Dropbox/data/