Openseadragon fixes

[marlo-longley]

Closes #3178
This was tested as part of a Spotlight application.

Changes:

1. the custom icons had stopped working because the ViewComponent was generating sequential ids (so 1-zoom-in 2-zoom-out) rather than using a consistent id for all control elements.

2. I wasn't able to get tests to pass without changes to the @presenter setup, which mimics the setup in the other ViewComponents.

2. In testing this work I found that multi-page items were rendering incorrectly. It seems that the options/params expected by OSD have changed: I needed to add sequenceMode: true, and I was able to remove other options that were set by default. Before (goes to last page and is just broken):

After:

[marlo-longley]

@jcoyne thank you for reviewing. I addressed your comments.