Add helpers to handle UUID<->str conversion

Converting UUID to string will be always in 128-bits format, but we can
accept to read 16-bits version (eg: 0xABCD).
Add search_svc command

With search_svc command, we can search services on remote device.
If we need a specific service, it's possible to filter by UUID that can
be 16-bits or 128-bits.
Add included command

After we find which services there are at remote device, we can
discover the relationship between them. The included command help us
with this, giving which services are included at specified service ID.