SEP-0011 Txrep implementation

• add SEP-0011 implementation (Txrep)
• add Txrep examples and test

Limitations: FeeBumpTransaction and muxed accounts are not yet supported - see also: stellar protocol issue #618

SEP-0011 MVP

• refactor transaction, move network passphrase to signing
• improve examples
• add SEP-0011 MVP (experimental)

SEP-0005: Key derivation

• SEP-0005 implementation:
• Key Derivation Methods for Stellar Keys
• Update documentation
• Add tests and examples

Federation (SEP-0002)

• SEP-0002 implementation - Federation
• update documentation
• add tests and examples

SEP-0001 - stellar.toml

SEP-0001 implementation added:

• loading and parsing stellar.toml data
• update documentation
• improve tests and examples

1.0.0 release

• update documentation
• improve tests and examples
• add tx_set_operation_count to ledger response
• finish beta testing phase

Improvements & bugfixes

• improve path finding
• improve trades query
• fix and improve order book query
• change offer ids from int to String
• improve tests and examples

Full muxed accounts support

• Handles muxed accounts on fee bump transactions (feeSource)
• Handles muxed accounts as transaction source
• Adds fee bump example
• Adds muxed account example

Support for muxed accounts

• Adds support for muxed accounts. You can now use muxed accounts in:
  -- PaymentOp.destination
  -- PathPaymentStrictReceiveOp.destination
  -- PathPaymentStrictSendOp.destination
  -- Operation.sourceAccount
  -- Operation.destination (for ACCOUNT_MERGE)

• Uses XdrMuxedAccount in all supported operations

fee stats - max fee - fee bump

• Add fee stats implementation
• Add max operation fee
• Fix fee bump transaction