v6.6.3

This release contains many major changes and improves. The most notable is the separation of insight-api and blockbook
handling into their own respective modules. The old implementation made only minimal changes to the original code
enough to get blockbook working in place of insight-api. Since InsightApiHelper made a lot of data-heavy queries from
the indexer, this inefficiency carried over to blockbook as well. With this module separation insight-api type indexers are
supported again. More importantly, re-implementation of BlockbookApiHelper makes the most efficient use of the available
RESTful endpoints reducing traffic per wallet loaded by a significant amount.

The second important change is migration over to Trezor's Ethereum blockbook. This removes the last dependency on coinquery.com
which was recently down giving 503 responses. It's still possible to use Etherscan.io but Ethereum blockbook indexer should be
preferred since it doesn't have the annoyingly low 5 api/call rate limit. Ethereum now has a gas fee selector as well as using gasnow.org
for gas price estimation.

The last notable change is PIN/Passphrase transitions. Getting all the panels to transition correctly in case of a PIN trigger turned out to be a trickier problem to solve. This is the third attempt at rectifying the problem. The core of the solution is to store the PIN trigger state somewhere and any panel that needs to know if it's transitioning from a PIN panel can just query this state.

Changes in this release:

• Removed Bitcoin Cash fork warning in sending panel. Replay risk is minimal at this point.
• Improved transitional behavior between PIN/Passphrase and other UI panels. See f29c825.
• Fixed PIN cancel rubberbanding issue with 'ReceiveAddress'.
• Rewrote large parts of BlockbookApiHelper making more efficient use of available endpoints.
  This refactor significantly reduces api traffic, reduces strain on indexing servers and improves wallet load times.
  See 9d0faa0 for implementation details.
• Updated some of the currency icons with right sizing and style.
• Updated Zcash BranchId to 'Canopy'. Signed transactions must have the latest branch id to be accepted by the network.
• Reorganized 'config.json' file into 'config.js'. Moved api token stuff out of 'background.js' into 'apitokens.js'.
  Edit 'apitokens.js' instead of 'background.js' if you need to configure and use a custom api key.
• Added gasnow.org for better Ethereum gas estimation.
• Implemented trezor blockbook api support for Ethereum. This removes any last remnant of dependency on coinquery.com.
  Note it's still possible to use etherscan.io for blockchain data purposes but not recommended due to its low 5 api/call rate limit.
• Added fee selector for Ethereum.
• Refreshing balance inside a coin wallet panel now only reloads balance for that coin instead of all coins in wallet list.
• Added Bitcoin TESTNET support. This allows for test sending&receiving of wallet without risking actual funds.
• Improved look and readability of transaction history window.
• Combined 'FeeService' stuff into 'coin-type' module for btc-style coins.
  This completes the refactor started with c287046.
• Fixed up CSS for send panel so error mesages don't shift UI elements.
• Added Syscoin support. This still needs firmware level support.
  If support of this coin is important to you feel free to pester KeepKey to merge this PR in.