Add Sidebar to Clean

[jdpigeon]

Add sidebar with instructions:
In the following screen, you will be able to visually inspect your data and determine which EEG channels and data segments should be excluded. Use caution - excluding too much data will not allow you to obtain interoperable results.
Each line represents an EEG channel. You will notice that some lines might be flat or very noisy. These lines probably correspond to EEG channels that did not make good contact with the scalp. Click on these lines to exclude them from further analysis.
You will also notice that your data has been divided into 1-second segments by vertical dashed lines. Some of these data segments should be excluded due to artifacts (e.g. eye blinks and head motion). Clicking on a data segment will change its color and mark it for exclusion. If you change your mind, click on the data segment again to unselect it.
When are done marking electrodes and data segments - close the ‘clean data’ window.