Split hnb_context,hnb_persistent,umts_cell_id to their own files

It's really disturbing having to cope with all HNB related code while
for instance focusing on CN side of things.
Properly split the HNB related code to its own files so it can be left
out easily when needed, or stuff found more easily when required.
It also makes it easier to extend it later.

umts_cell_id is split to its own module since it's needed both in
hnb_context and hnb_persitent, and it's really independent of everything
else in the code.

Change-Id: I4ff65d14f94d99a57316c2483c92244078bb5dd9
---
M include/osmocom/hnbgw/Makefile.am
M include/osmocom/hnbgw/context_map.h
A include/osmocom/hnbgw/hnb.h
A include/osmocom/hnbgw/hnb_persistent.h
M include/osmocom/hnbgw/hnbgw.h
M include/osmocom/hnbgw/hnbgw_hnbap.h
M include/osmocom/hnbgw/hnbgw_rua.h
A include/osmocom/hnbgw/umts_cell_id.h
M src/osmo-hnbgw/Makefile.am
M src/osmo-hnbgw/context_map.c
M src/osmo-hnbgw/context_map_rua.c
M src/osmo-hnbgw/context_map_sccp.c
A src/osmo-hnbgw/hnb.c
A src/osmo-hnbgw/hnb_persistent.c
M src/osmo-hnbgw/hnbgw.c
M src/osmo-hnbgw/hnbgw_hnbap.c
M src/osmo-hnbgw/hnbgw_ranap.c
M src/osmo-hnbgw/hnbgw_rua.c
M src/osmo-hnbgw/hnbgw_vty.c
M src/osmo-hnbgw/kpi_dtap.c
M src/osmo-hnbgw/kpi_ranap.c
M src/osmo-hnbgw/nft_kpi.c
M src/osmo-hnbgw/osmo_hnbgw_main.c
A src/osmo-hnbgw/umts_cell_id.c
M tests/ranap_rab_ass/ranap_rab_ass_test.c
M tests/umts_cell_id/umts_cell_id_test.c
26 files changed, 1,224 insertions(+), 1,006 deletions(-)