• Add types for LedgerCallBuilder.ledger.
• Add types for Server.operationFeeStats.
• Add types for the HorizonAxiosClient export.
• Move @types/* from devDependencies to dependencies.
• Pass and use a stream response type to CallBuilders if it's different from the
  normal call response.
• Upgrade stellar-base to a version that includes types, and remove
  @types/stellar-base as a result.