Bbc1

* ID truncation (ID length less than 256-bit) support
* X509 certificate for public key
* KeyPair class in bbclib.py can receive X509 self-signed certificate
* ECC Prime-256 v1 support for private/public key
* libbbcsig is decoupled to https://github.com/beyond-blockchain/libbbcsig
* default config is introduced
* search count upper limit is configurable
* Extend transaction search functions (94)
* Bug fixes

* Bug fixes
* pip install bug is fixed but pipenv install still has some troubles.
* Bug of serialization/deserialization of BBcSignature in some cases is fixed

* Restructure the whole package
* Only bbc1/core/ remains
* Ledger_subsystem related codes and libraries are separated into other repositories
* Support BSON (binary JSON) format for transaction data structure
* Documents are updated
* Utilities are re-designed
* Bug fixes

* The core part is totally re-designed
* user_message_routing.py, data_handler.py, topology_manager.py, key_exchange_manager.py, key_exchange_manager.py are newley added
* inter-nodes and core-app communications are secured by AES256 encryption
* Implement domain/node key verification for administrative messages
* Scheme for recovery of forged transaction data is modified
* A user (bbc_app) explicitly triggers the recovery when it obtains forged transaction data
* Anycast support
* Add currency library (token_lib)
* Add a new search method to obtain series of transaction data
* Cross_ref support

* Add libraries for token and id management

* Change APIs in bbc_app.py (remove asset_group_id options)
* Modify schemas of bbc_ledger tables
* Introduce BBcRelation/BBcPointer/BBcWitness class as parts of BBcTransaction
* Fix several bugs