Make references to Adapter/Interface consistent

The disambiguation term `Interface` was introduced rather hastily during the communication layer redesign and 1.0 release.

Consequently, a lot of back-end code still uses incorrect terminology. This should be updated to be consistent throughout.

Terminology:
- `Adapter`: Functionality provided by the framework to abstract interaction with shared _transport_ protocols (EPICS, TCP Stream, etc).
- `Interface`: Functionality provided by simulated device to implement specific _device_ protocol(s) based on adapter(s).

Terminology should be updated in code, as well as comments and documentation headers.