* rename cdbus header include guards to use CDBUS_ instead of LASH_DBUS_
* remove dbus/error.h and dbus/error.c
error.h contained lash/ladish specific error strings and
lash_dbus_error() prototype. lash_dbus_error() is renamed to
cdbus_error() and its implementation is moved to dbus/method.c. The
D-Bus error strings that have DBUS_ERROR_XXX matches are removed and
their uses are switched to the libdbus variants. The ladish specific
error strings are moved to dbus_constants.h