* display chain/network in header if not mainnet
* indicate active chain/network in startup log
* specify which chain/network "fun" items apply to and only show them for that chain
* don't display exchange rates for testnet/regtest
* use block interval of 150 for regtest halving
* regtest hacks: since getblockchaininfo.blocks=0 on a default regtest node despite the genesis block existing, hack in a couple of places in order to display the genesis block
* fix /peers page to not throw error with no connections
Move closer to the original vision of supporting any address-querying implementation desired. Current options include ElectrumX (as before) and now blockchain.com and blockcypher.com since they were easy to support and are publicly/easily available (though ridiculously neither is yet to support bc1 addresses).
- new env var option BTCEXP_ADDRESS_API, value can be electrumx, blockchain.com, blockcypher.com
- update ElectrumX client connect to request v1.4 of API as all clients are now supposed to do
- misc frontend improvements/cleanup for addresses
- footer: full-width to match header; remove bottom border
- extraneous padding removed from some tx lists
- fix some card-body wrapping issues for paginations at bottom
- pull in chart.js and add integrity attribute
- move common tx-stats code to utils
- use bootstrap progress bars for block fullness in blocks-lists (moving away from radial progress which includes too much css and can be finicky)
- clean / reorg frontend code for graphs and homepage network summary