libsmbconf: add smbconf_create_set_share

libsmbconf: add smbconf_create_set_share

This call creates a new share definition, using the parameters provided
with a smbconf_service structure.
Such an interface allows for simple cloning of services with:
smbconf_get_share(conf_ctx, mem_ctx, base_sharename, &base_service_def);
base_service_def->name = clone_sharename;
smbconf_create_set_share(conf_ctx, base_service_def);

Pair-Programmed-With: Michael Adam <obnox@samba.org>

Signed-off-by: David Disseldorp <ddiss@samba.org>
Signed-off-by: Michael Adam <obnox@samba.org>