suggestion to add GRAPHENE_BLOCKCHAIN_NAME to config

User Story As a graphene fork and bitshares blockchain developer I want the name of the blockchain to be added to config so that client programs i write can display the info to their users.

Global var can be added at https://github.com/bitshares/bitshares-core/blob/master/libraries/chain/include/graphene/chain/config.hpp#L26 and displayed initially just in the info wallet call at: https://github.com/bitshares/bitshares-core/blob/master/libraries/wallet/wallet.cpp#L548

I think this will be also be displayed automatically at https://github.com/bitshares/bitshares-core/blob/master/libraries/app/database_api.cpp#L623

Another spot can be as an initial title banner when witness node is started. Currently when the chain is new a banner "Welcome to graphene" is displayed. Displaying the blockchain name when chain is not new can be a good idea.

Looking for comments.

Impacts Describe which portion(s) of BitShares Core may be impacted by your request. Please tick at least one box.

• API (the application programming interface)
• Build (the build process or something prior to compiled code)
• CLI (the command line wallet)
• Deployment (the deployment process after building such as Docker, Travis, etc.)
• DEX (the Decentralized EXchange, market engine, etc.)
• P2P (the peer-to-peer network for transaction/block propagation)
• Performance (system or user efficiency, etc.)
• Protocol (the blockchain logic, consensus, validation, etc.)
• Security (the security of system or user data, etc.)
• UX (the User Experience)
• Other (please add below)