Adds gapLimitOptions

[coreyphillips]

This PR:

• Adds ability to adjust gap limit lookBehind and lookAhead.
• Implements multiple scanning strategies for getUtxos method.
• Ensures we continue monitoring addresses with UTXO's outside the gap limit in the event it receives additional Bitcoin.
• Updates getNextAvailableAddress method to account for aforementioned changes.
• Adds tests for gapLimitOptions.
• Bumps version to 0.0.23.