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
some cleanup and some small improvements to get/set
interim
minor cleanup
some speedup in invalidate_deps
sped up update_destvar
fixed bug in set_indexed_value
Merge pull request #1608 from naylor-b/perf2

various performance improvements