Move to seurat 4

[pcm32]

Moves Seurat script to Seurat 4.0 (higher versions have issues with some of the IO conversions, so I intend to park it here, release, and then fix issues with later seurat versions).

A lot of new tools, automatically written, through the cli generator:

• Integration, which does most of the steps in the single cell integration vignette from Seurat (for user convenience).
• Auxiliary integration methods: map query, find conserved markers, select integration features, classify against reference, split objects (needed for tests).
• Seurat 4 convert, providing the ability to convert multiple formats through Seurat
• Run UMAP (this seems to have indentation issues of the first versions of cli generator, but this one is now part manual, part automatic, so tricky, I could try to rewrite automatically and see if all tests are ok).
• Seurat plot: enables the 5 or 6 types of plots available in the plotting vignettes from Seurat. They all can produce a ggplot2 RDS object which an then be further shaped (or used with hover locator in the scatterplot cases).
• Hover locator: this is cool, produces interactive XML which allows to inspect cell by cell.
• YAML files for the automatic generation of these R scripts + Galaxy wrappers through the cli generator
• Tests for all new scripts, plus any updates needed for Seurat 4 for the existing ones (including default changes where dectected).

To be merged after #23