Allow for undo burst functionality (#36)

[colebillys19]

Implemented 'undo burst' functionality (issue #36).

Summary:

• added functions to get and set calculator state to the calc-helpers file
• mapped frame and frameIDs (from the images state slice) to the Burst component's props
• changed the Burst component's local state to include prevFrames, prevFrameIDs, and prevCalcState to allow for undo
• in handleRequestBurst, im grabbing these three values prior to burst capture
• if the capture is successful, the data is saved in local state
• if unsuccessful, data is not saved
• also added isCapturing to local state to trigger UI change when burst is being captured... capture button changes to 'capturing...' and is unclickable
• when a burst has been captured, an undo button appears in the UI
• added undoBurst action creator, UNDO_BURST action type
• added handleUndoBurst method, dispatches action and reverts calculator

[colebillys19]

Jason pointed that the undo burst button was not showing when you capture a burst with no frames previously captured. This was because the render method for Burst is conditionally rendering the button based on whether or not there were frames in state before the capture. Not the best logic. I added a straightforward boolean called canUndo that is used to check whether or not the button should be rendered. This is set to true on burst capture, and set to false on undo.

[japamat0]

With some of your nicely named function names, some of these comments may not be necessary :)

[colebillys19]

Done

[japamat0]

Comments may not be necessary for these functions, they are perfectly described by their name

[colebillys19]

Done

[misscoded]

It's possible to interrupt the capture mid-way through processing with the 'UNDO' button, resulting in only a partial burst. I wouldn't display the option to undo until the burst capture has been completed.

[colebillys19]

Fixed

[colebillys19]

I also added a componentDidUpdate to the burst component to check when new frames (individual frames) are added to state after a burst is captured. This way once a user captures a new frame with the camera button, indicating they're happy with the burst, the undo burst button goes away.