presets pane design

[bill-auger]

feature of epic #31

the "Presets" pane currently overlaps exactly with the "Controls" pane

the back page "Presets" pane includes the following widgets that are always active:

• presets dropdown menu - (select preset configuration)
• config toggle - (re-enable all enabled capture and/or output - replace "Presets" pane with "Controls" pane and replace "Config" pane with "Preview/Chat" panes)

it also includes the the following widgets that are currently always active:

• save button - (store configuration changes to the current preset)
• new button - (create a new user-defined preset)
• delete button - (delete a user-defined preset)

but ideally the save, new, and delete buttons should be enabled only when appropriate changes are pending

NOTE: that currently the presets dropdown menu and config toggle are exact duplicates of those on the "Controls" pane in form and function - ideally there would only be one set of these this entire panel could be integrated with the "Config" pane