Invert order of brew install omero and omero_homebrew.sh

With the recent modifications in homebrew-alt, most dependencies should be handled in the OMERO formula.
Remove Homebrew dependencies from omero_homebrew.sh

With recent changes to the OMERO formula, the pure Homebrew dependency are
directly handled by Homebrew. This script should still check and install the
Python dependencies of OMERO.
Convert deprecated omero_homebrew.sh into python_deps.sh
Strip remaining Homebrew components from python_deps.sh

Update OMERO-homebrew-install to use correct location for dependencies
Add notes about Python package dependencies (Scipy, PyTables)
Add note about the expected current directory
Check for local bin/pip installation before looking in the PATH
Merge pull request #791 from sbesson/rebased/develop/homebrew_deps

OMERO homebrew dependencies (rebased onto develop)