remove base_kernel_url
add InlineBackend.print_figure_kwargs

removes special handling of 'quality', in favor of passing arbitrary kwargs to fig.canvas.print_figure.

This lets people override the occasionally problematic use of `bbox_inches='tight'`,
and any potential future issue that might be solved by adding/changing kwargs to print_figure.
Some template static_url tweaks

- don't try to include version in static_urls that don't point to files
- use full static_urls (with extension) for backbone and underscore, so version can be computed

closes #5141
Simplify implementation of TemporaryWorkingDirectory.

Closes gh-5160
remove mktemp usage

mktemp is insecure, by the time the generated filename is used someone
else might have modified it.
Merge pull request #5166 from juliantaylor/mktemp-remove

remove mktemp usage
Merge pull request #5163 from takluyver/i5160

Simplify implementation of TemporaryWorkingDirectory.
Merge pull request #5100 from minrk/base_kernel_url

remove base_kernel_url
Merge pull request #5147 from minrk/static-url-version

Some template URL changes
fixup
test select_figure_formats
remove InlineBackend.quality from whatsnew
add print_figure_kwargs to whatsnew
read InlineBackend defaults in set_matplotlib_formats
specify default bbox_inches in print_figure explicitly

to preserve legacy behavior for any direct callers
test display.set_matplotlib_formats

give set_matplotlib_close default close=True
remove redundant check for self.shell is None
generate supported formats in ValueError
Merge pull request #5110 from minrk/bbox_inches

add InlineBackend.print_figure_kwargs