Use in-place caching by default in Memoizer

This commit sets the in-place caching attribute to `true` in the constructors not passing a `directory`. The in-place constructor using a boolean value now becomes obsolete and is removed. Unit tests are added for each supported constructor using `getMemoFile()`.

Couple of questions:
-  should we keep `Memoizer(0, null)` as as way to create a no-op Memoizer?
- what are the consequences of this change on consumers like OMERO?

--no-rebase
will to change these to `new {@link ImageReader}`?