Phconvert

What's new?
- Try to address h5labview issue with empty strings by saving a single-space string in empty descriptions. See 4.

What's new?

Backward-incompatible changes:
- Change `dye_names` from array of string to a single string containing CSV text (8421904505fd12114d3877c6f6c965d8703e7862). Closes 2.

Other changes:
- Docs improvements

What's new?

This version adds type checks when saving Photon-HDF5 files as described in this [Pull Request](https://github.com/Photon-HDF5/phconvert/pull/3).

In this version a few fields have been renamed and a few were added:
- `acquisition_time` -> `acquisition_duration`
- `comment` -> `description`
- `funding` (new field)
- `license` (new field)

Additionally:
- The notebook to convert files have been updated to be easier to follow for users new to Jupyter.
- The default URL saved in the file is now http://photon-hdf5.org

What's new?
- Still one forgotten rename (e05873a08f1e22163cfaa2695fe2699d55e3df62)

What's new?
- Finish renaming some fields forgotten in the previous release (bd4032d1b0667e13fed3f885191298e4468eb8fe).