Memoizer: Persist caching to sub readers

[dgault]

Initial PR for testing and discussion of a possible option for passing Memoization to sub readers. In this case each reader must wrap its sub readers, which leaves a significant amount of testing required to cover the large number of readers involved.

• MetadataOptions used to store Memoizer otpions
• A wrap method in Memoizer to handle the wrapping
• Each reader then wraps its sub readers

Likely to be further commits to bring this more inline with the IDR branch New MetaxpressTiffReader also needs to be updated

[joshmoore]

First off, wow. I find this very exciting. I only ever approached propagating to the most necessary readers in the IDR context.

I do wonder if we're doing this across the board now if there are any other wrapping concerns we should consider. I imagine that might work by letting the Options object decide which wrappings to apply.