mcf: change layout of build directories

  1) use only one BUILDDIR for all machines, no need to build/store
     native sysroot for each machine in separate BUILD-MACHINE even
     when sstate-cache is reused
  2) rename bitbake.rc to oe-init-bitbake-build-env and allow users
     to source them and then call bitbake directly e.g.
     "bitbake -k webos-image" instead of using Makefile
  3) merge functionality of toplevel Makefile and BUILD-MACHINE/Makefile
     to single Makefile and reuse oe-init-bitbake-build-env to have all
     settings in only one place
  4) use TOPDIR instead of PALMDIR [OWEBOS-2487]
  5) conf/local.conf and bblayers.conf are now in toplevel directory and
     also shared by all MACHINES (weboslayers.py is also global)
  6) use MACHINE/DISTRO from shell environment, allows easy iteration over
     MACHINEs e.g.
     for MACHINE in qemuarm qemux86 qemux86-64; do
       export MACHINE;
       bitbake -k webos-image;
     done
  7) this layout is similar to layouts used by other distributions and
     default layout
  8) install and installnew target doing rsync of .ipk files was
     renamed to deploy and deploynew because it was conflicting with
     install* targets for bitbake

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@palm.com>
Change-Id: Ica7ade8921bece8ff85ffb61f0d33d8636009838