Better static tables

[Jolanrensen]

Based upon #513, this fix adds better static tables with uncollapsed column groups as well as interactive frame columns using <details> (without JS and optional CSS).
This allows ipynb notebook files to be viewed by simple renderers that don't allow iFrames or JS to be run (such as GitHub). Note that Github strips out the CSS and <details> tags and displays the nested DataFrames in full, so I made sure the limits for nested dataframes were reasonable.
This means: We adhere to the given rowsLimit and nestedRowsLimit (20 and 5 by default respectively) for the top-level and we halve the nestedRowsLimit (rounding up) for each deeper nested DF.

I also updated all notebooks except for the json one (it's too large for GH now)

[Jolanrensen]

Okay, outside of Github, this static rendering works great, however, Github cannot render anything even smelling interactive. I tried CSS tricks, <details>, but it doesn't help. CSS just doesn't do anything, as well as JS.
So, this is the result we get... What looks better in your opinion?

Before:

After:

Before:

After:

Before:

After (too large to fit, but is scrollable):

[koperagen]

Ok, i think i understand what's going on in that matrix creation. Looks good! Few suggestions: move implementation to staticHtml.kt, there's now a lot of specific things not related to regular HTML. Second, have you checked escaping? toHTML does escape symbols, maybe cellFormatter that is used will do it, not sure

[Jolanrensen]

@koperagen Thanks! I'll move it to another file.
As for escaping, yes, that's done by this line:
append(cellRenderer.content(cellValue, configuration).truncatedContent)
The CellRenderer calls renderValueForHtml() which uses the formatter :).

Edit: Okay rebasing on master caused all these extra commits to appear... fun