Merge pull request #5 from treww/master

Little refactoring and build fix.
Fix GetChild error with string argument
added many missing const ref decl
adapt to restructure from treww
readme update
Merge pull request #6 from oroulet/master

Fix GetChild error with string argument
exposed subscription interface, not tested yet but compiles
add some comments so server example
expose high level subscription interface, tested as much as possible but broken until we add async support
small cleanup
add subscription test, enable subscription in client example
Merge branch 'master' of https://github.com/FreeOpcUa/opcua-python
Merge pull request #7 from oroulet/master

expose high level subscription api to python
update to apichange and draft event support
port to subscirption using unique_ptr
python callback finally working!
cleanup
small cleanup
add test for deleting monitoreditem
Merge pull request #8 from oroulet/master

enable callback, prepare for event support