Czitools

- smaller subclasses
- allow to install czitools with minimum dependencies

* allow reading CZI using zoom factor and using http links
* bugfixes
* more and improved tests

- bugfixes
- new treewidget to display metadata
- code cleanup

- reading CZI as 6d array now uses dask delayed reading for individual 2d planes (inspired by [pr4deepr](https://github.com/pr4deepr)
- renaming functions
- updates demo scripts and notebooks
- bugfixes

- more tests
- different way to store objective metadata to account for more than one objectives
- removed cztile requirement

* refactoring
* additional and improved tests