Implementation of monero_wallet_light

[everoddandeven]

This pull request introduces a new class, monero_wallet_light, which is designed to facilitate the connection and interaction with Monero light wallet servers. The monero_wallet_light class provides essential functionalities such as:

1. Connecting to a light wallet server to fetch wallet data without needing the full blockchain.
2. Synchronizing wallet balances and transactions in a lightweight manner.
3. Sending transactions through the light wallet server.
4. Querying necessary blockchain information from the server.
5. The purpose of this implementation is to improve the user experience for devices with limited resources, such as mobile devices, by offloading blockchain-heavy operations to remote light wallet servers.

Closes #58

[woodser]

Getting this warnings on the build:

/Users/woodser/git/monero-java/external/monero-cpp/src/wallet/monero_wallet_light.cpp:1368:11: warning: logical not is only applied to the left hand side of this comparison [-Wlogical-not-parentheses]
      if (!kv.first == account_index) continue;
          ^         ~~
/Users/woodser/git/monero-java/external/monero-cpp/src/wallet/monero_wallet_light.cpp:1368:11: note: add parentheses after the '!' to evaluate the comparison first
      if (!kv.first == account_index) continue;
          ^
           (                        )
/Users/woodser/git/monero-java/external/monero-cpp/src/wallet/monero_wallet_light.cpp:1368:11: note: add parentheses around left hand side expression to silence this warning
      if (!kv.first == account_index) continue;
          ^
          (        )