Add 'make install' supporting DESTDIR and SCRIPTSDIR

DESTDIR: staging directory for a package
SCRIPTSDIR: directory into which to place volume/ and datapath/ subdirs

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Add CHANGES file

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Update README.md, CHANGES

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Merge pull request #14 from djs55/python-dir

Add 'make install', update docs