Draft: blissdata: Few changes on blissdata+beacon+demo

This PR:

• Simplifies BeaconFiles method names
• Implement get/post command to create a key/value storage in Beacon server
  • Implement get/post from BeaconFiles and map the key/value Beacon storage
• Put DATA_ROOT from the demo session inside Beacon
• Put TANGO_HOST from the demo session inside Beacon

The idea here is to reduce the demo session command line

Some commits are related to #1837 (closed)

From:

DEMO_ROOT="/nobackup/lvalls1/valls/workspace/bliss.git/demo" TANGO_HOST=lvalls:10000 BEACON_HOST=lvalls:10001 bliss -s demo_session

To:

BEACON_HOST=lvalls:10001 bliss -s demo_session

The beacon server should already know everything.