pm-graph: package makefile and man pages

update help text and man pages for both tools
- added more examples and separated them by category
Makefile upgrades
- uninstall: remove errors from uninstall if tool not found
- install: perform uninstall before install

Signed-off-by: Todd Brandt <todd.e.brandt@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>