Misc doc updates..

[rrw-zilliqa]

Sorry - a rather brief description!

• Accommodate the changes in Documentation changes zq2#1434 - in particular, fix a renaming bug where sequences matching the prefix didn't rename properly.
• Put a button in the zq1 section header to take users to Zilliqa 2
• Change title to Zilliqa 1.0 Developer Portal
• Remove the Zilliqa 1.0 landing page and redirect to basics/blockchain-basics/basics-intro-blockchain/
• Make the default landing page for the constructed site Zilliqa 2