Remove unused method 'string_to_bool' from utils

The method 'string_to_bool' in utils is not used.
Furthermore, if we need this method in the future,
we should use 'bool_from_string' from oslo cliutils
to replace it.

partially implements blueprint common-client-library-2

Change-Id: I21978d389a8721a40e1669351575297ce61a438e
Add support for build info API

Add new command to interact with the build info API and return build
revision information.

Closes-Bug: #1267586
Change-Id: Iea501cea4ddfd0a9f463299f71b72795a93e4def
Updated from global requirements

Change-Id: If173908ddb06a946f68fd27db1248f4974033c8c
Merge "Remove unused method 'string_to_bool' from utils"
Merge "Updated from global requirements"
Merge "Add support for build info API"