brought over some stuff from earlier performance branch
caching _all_child_vars
caching boundary inputs/outputs
caching srcs and boundary vars
caching for list_connections
cleaned up some config_changed stuff
Merge branch 'perf2' of github.com:naylor-b/OpenMDAO-Framework into perf2
Merge branch 'dev' of github.com:OpenMDAO/OpenMDAO-Framework into perf2
little speedups
some cleanup
cleanup:
Merge pull request #1605 from Kenneth-T-Moore/bench

Fix for bug where objective was deleted during component replace.
another bug
Merge branch 'dev' of github.com:OpenMDAO/OpenMDAO-Framework into bench
Merge pull request #1606 from Kenneth-T-Moore/bench

Another bug fix
some cleanup and some small improvements to get/set
interim
minor cleanup
some speedup in invalidate_deps
sped up update_destvar