Developer Workflow Improvements

Developer workflow improvements as documented in the following bugzilla entry:

Todo list

Properly report failures in bitbake execution during install (output is currently discarded)
Prevent do_rootfs itself from executing on install - we only need the tasks that it depends upon
Write test script for SDK
Randy: getting errors from bitbake about changed signatures - behaviour change after Hongxu's patch?
Update environment setup script to use buildsystem toolchain -- Done but needs testing and function dependent on uninative - Randy
Fix runqemu(and possibly other tools?) since we no longer have the nativesdk sysroot (Add them to buildtools-lite?)
Refactor to move functionality to SDK classes rather than meta-newsdk recipe
nativesdk-qemu-helper_1.0.bb and qemu-helper_1.0.bb don't publish the same set of files. Investigate, since runqemu(and possibly other things) may need to come from the buildsystem's native sysroot.
Installing the sdk to /opt requires root perms, but if you run the installer under sudo/as root then the inner execution of bitbake to prepare the SDK fails at sanity check
uninative-tarball errors when restoring from sstate (should it even try?)
uninative-tarball reports "WARNING: Function doesn't exist" during build
Error when running recipetool from devtool "Error: The OE SDK/ADT was detected as already being present in this shell environment. Please use a clean shell when sourcing this environment script." - probably need to bypass this check via an extra environment variable

Add support for plugins in multiple layers
Support 'devtool modify linux-yocto' - externalsrc doesn't seem to work here at the moment -- Started, paused until Bruce's patchset is ready - Paul
Add an option for modify / add to use the same directory for source and build where that's required