Add first attempt for support libelasto stored backend.
Rebuild configure and config.h.in
Disable object storage devices for now.

Until we crack the problem of writing/reading to S3 using the droplet
library disable the use of these kind of devices.
Disable elasto storage devices for now.

Until we crack the problem of writing/reading to Azure using the
libelasto_file library disable the use of these kind of devices.