Add find_config_nodes function

Used to walk the parse tree based on an expression

Signed-off-by: Jim Lieb <jlieb@panasas.com>
Extend AddExport DBUS method to include a expression argument to identify the export

Signed-off-by: Jim Lieb <jlieb@panasas.com>
Extend manage_exports script and ExportMgr class for AddExport

Signed-off-by: Jim Lieb <jlieb@panasas.com>