Auto collect tiled mosaic

[campagnola]

Some way to automatically collect a tiled mosaic covering an entire slice

• Autofocus
• Find boundaries
• Fill mosaic
• Store as one .ma file or one folder full of images
• Metadata: which slice is this a picture of?

[campagnola]

As part of this, the image sequencer used to collect Z stacks should be extended to allow xy mosaics as well. Ideally it should be possible to take a z stack at each location as well.
It probably won't be useful to try to do fast xy scanning the same way we collect fast z stacks.

[outofculture]

• make a shared api for CameraInterface and Camera(Device) that can be passed into the sequencer or anywhere else that wants Frames.
• teach Frame to append to an existing file.
• put the background-saving logic into a Frame object.
• fix the background-saving bug that would occur if two images got saved into different folders that nevertheless share a background.
• teach MultiPatchLog to display image sequences