Name and in-page extension API cleanup

[da-kami]

Make sure that the names make sense:

• Waves = the web application the user sees ^= the fontend the lender serves and the borrower uses ^= the product?
• "Extension" = the complete extension (including the wallet + backup functionality)
  • The interface def in Waves is called "WavesProvider" which is confusing
• Bobtimus = the lender backend

Waves + Bobtimus is shipped / deployed together so we can change APIs easily.
The Extension is shipped separately - so the interface between Waves and Extension is critical and breaking changes will require the user to take action (i.e. install a new Extension version). Thus, we should have a look at the API and see if we want to change things before going into production.

[da-kami]

waves => fronted
extension => extension

wavesProvider => provider / walletProvider