bitbake: toaster: build control functionality

bitbake: toaster: build control functionality

We add the build control functionality to toaster.

* The bldcontrol application gains bbcontroller classes
that know how to manage a localhost build environment.

* The toaster UI now detects it is running under build
environment controller, and update the build controller
database and will shut down the bitbake server once
the build is complete.

* The toaster script can now run in standalone mode,
launching the build controller and the web interface instead
of just monitoring the build, as in the interactive mode.

* A fixture with the default build controller entry for
localhost is provided.

[YOCTO #5490]
[YOCTO #5491]
[YOCTO #5492]
[YOCTO #5493]
[YOCTO #5494]
[YOCTO #5537]

(Bitbake rev: 10988bd77c8c7cefad3b88744bc5d8a7e3c1f4cf)

Signed-off-by: Alexandru DAMIAN <alexandru.damian@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>