This commit contains work done by Eurecom and by Benetel.

- reworked configuration file and configuration for gNB (write directly to ASN1 structure from config module instead of passing intermediate structures)
- added prach procedures for gNB with configuration of PRACH L1/L2 parameters

But NR-RRC-Definitions.asn file only include the NR-RRC-Definitions DEFINITIONS section
If we include the NR-UE-Variables into asn file, it will can't be compile in asn tool
and also some of implict problem for new version asn file

-Amend do_ServingCellConfigCommon function

- Create PDCCH structre in FAPI, it will be one of P7 structure
- Maintain Configuration Module

'_' is not a valid character.

S1AP specs say:

    ENBname ::= PrintableString (SIZE (1..150,...))

And X.680 (08/2015) 41.4 table 10 lists the valid characters for
PrintableString. '_' is not there. We replace by '-' which is there.

Connection of eNB to ppenair-cn has not been tested. There is no reason
why it would fail.