Developer Workflow Improvements

Developer workflow improvements as documented in the following bug:

https://bugzilla.yoctoproject.org/show_bug.cgi?id=6662

Todo list

• Running recipetool from devtool within the SDK seems to be broken:

 paul@peggleto-mobl5:~/poky/newsdk$ devtool add pv ~/tmp/pv-1.5.3/
/home/paul/poky/newsdk/layers/poky/oe-init-build-env
Traceback (most recent call last):
  File "/home/paul/poky/newsdk/sysroots/x86_64-pokysdk-linux/usr/bin/devtool", line 407, in <module>
    ret = main()
  File "/home/paul/poky/newsdk/sysroots/x86_64-pokysdk-linux/usr/bin/devtool", line 400, in main
    ret = args.func(args)
  File "/home/paul/poky/newsdk/sysroots/x86_64-pokysdk-linux/usr/bin/devtool", line 223, in add
    create_recipe(srctree, args.recipename)
  File "/home/paul/poky/newsdk/sysroots/x86_64-pokysdk-linux/usr/bin/devtool", line 120, in create_recipe
    stdout, stderr = exec_build_env_command(config.init_path, basepath, 'recipetool create %s %s' % (recipefile, srctree))
  File "/home/paul/poky/newsdk/sysroots/x86_64-pokysdk-linux/usr/bin/devtool", line 133, in exec_build_env_command
    return bb.process.run('%s%s' % (init_prefix, cmd), **options)
ExecutionError: Execution of '. /home/paul/poky/newsdk/layers/poky/oe-init-build-env /home/paul/poky/newsdk > /dev/null 2>&1; recipetool create /home/paul/poky/newsdk/workspace/recipes/pv/pv.bb /home/paul/tmp/pv-1.5.3' failed with exit code 127:
/bin/sh: recipetool: command not found

• Prevent do_rootfs from executing on install
• Modularise devtool -- Paul: in progress
• Write test script for SDK