Source code for labbench 0.20 release

This is the source code package for the labbench python module, version 0.20, which is its first public release. The purpose of labbench is to streamline and organize complicated laboratory automation tasks that involve large-scale benchtop automation, concurrency, and/or data management. It is built around a system of wrappers that facilitate robust, concise exception handling, type checking, API conventions, and synchronized device connection through python context blocks. The wrappers also provide convenient new functionality, such as support for automated status displays in jupyter notebooks, simplified threaded concurrency, and automated, type-safe logging to relational databases.