[Refactor] Clean up wallet related code

[panleone]

Abstract

This is a continuation of the work started in #197 main changes are:

• From now on Masterkey has the only role of internally generating addresses and keys without any context, all external information, for example number of generated addresses, map of known addresses, nAccount used in derivation path has been moved to the Wallet class
• Having account info only stored in Wallet instead of spread in all files is also a first step toward multi account system.
• I cleaned up almost all files and removed functions that should be called only internally from the Wallet class: for example getDerivationPath() and getMasterKey()
• Wallet class has been decoupled from GUI
• Network class takes now a Wallet object instead of a Masterkey

Overall, as you can see from the git diff, I think that this is a good clean up and from this point we should finally be able to build a good Wallet class that will also manage UTXO, masternode, balance...

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Testing

Test all features related to wallet:

• Create a new wallet
• Check that you can send and receive funds
• Check that you can generate new addresses
• Check that the contact system works
• Check that you can encrypt the wallet and change password

If any errors are found, the PR works unexpectedly, or you have viable suggestions to improve the UX or functionality of the PR, let me know!

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For future contributions

While the clean up is almost completed there are still a few places that can be improved: for example

• In bitTrx.js there is still a call to wallet.getDerivationPath()
• the Masternode class should also be refactored and incorporated with the new Wallet class

[Duddino]

I like how the new Wallet class works, however there seems to be an exception when you open MPW, other than that I've left some minor nitpicks

[panleone]

implemented the review and fixed the problem on opening

[Liquid369]

tACK 893afd2
Working as per tests

[Duddino]

tACK

[JSKitty]

tACK ac66fcd

Tested every suggested Test area, tried new wallets, existing wallets, etc, not an issue.

This cleanup has gotten our wallet/key handling code in a much nicer state that I've been wanting for a while, really glad this was handled, on the way to a cleaner and more stable MPW! 🚀

[Duddino]

tACK I like the new wallet class

[Liquid369]

tACK ac66fcd