Added the ability to record a pause command through CTRL+SHIFT+B

This pull request does the following:

1. It adds the ability for test developers to add a ```PausePlaybackCommand``` through the use of shortcut key ```CTRL+SHIFT+B``` while they are recording a session.

2. It addresses a review comment [in a previous pull request](https://github.com/DynamoDS/Dynamo/pull/1231)