Merge accounts package into connector package

[cairin]

Problem

The current implementation of the accounts and connector packages is conflicted. They are implemented as separate packages. However, the accounts package is being imported into the connector package as if it were a module, when it is implemented as a standalone service.

Constraints

• The connector logic and the ilp accounts logic should be separate.
  • They should be isolated services.
• The connector service imports types from the accounts service.
• The connector and accounts service should communicate in-process for performance.

Proposal

This proposal follows from #52, to be implemented alongside/after.

The connector package should be renamed the interledger package, and the accounts logic (currently in the accounts package) should be implemented as a service within the new interledger package.