5.2.1 EMG patch

[retiutut]

• Closes Map channels to EMG Joystick inputs #1156
• Closes Fix vertical alignment of pop-up text and buttons #1157
• Closes Rename "smoothing" to "window" in EMG Settings #1158
• Closes Add EMG joystick to session settings #1159

Bump version to 5.2.1

[retiutut]

[philippitts]

• It looks like the EMG settings buttons might still be a little off center. I recommend moving them up a little bit (see screenshot).
• I think the header text may be a little too big. At first glance, it's a little hard to tell that the header text is related and aligned to the columns and not just one big line of text. I think taking the font down a few sizes would help with this.