Update TestTools

Changes:

• Add support for connecting wallet to remote node
• Add passing command line arguments to wallet
• Fix random fail on CI related to implementation of empty directory removing
• Update existing tests to use new TestTools interface
• Make current directory available to user (via context.get_current_directory())
• Remove main net singleton

Internal changes:

• Make wallet independent from World
• Introduce user handles for Wallet and RemoteNode
• Add internal library helper Url for url parsing and serializing