Update .gitignore and .editorconfig

[cbeams]

This PR introduces two non-code related changes:

368f0ad7f (Chris Beams, 5 weeks ago)
   Ignore Structure101 Workspace files

   In the refactorings that will follow, Structure101 Studio and the
   Structure101 Workspace IDEA plugin will be used to visualize and help
   resolve tangles in the codebase. We were already ignore Studio
   configuration files which end in .java.hsb, and this commit ignores the
   newer Workspace product's .java.hsw files as well.

b4ee9d33e (Chris Beams, 3 weeks ago)
   Do not strip trailing whitespace in Git diffs

   Problem: Editorconfig was configured to strip trailing whitespace in all
   file types. This is generally a good thing, but when interactive rebasing
   with Git and editing the contents of a commit, trailing whitespace is
   significant on blank lines and must be preserved in order for edits to be
   applied cleanly.

   Solution: Update Editorconfig to exclude *.diff from the strip whitespace
   rule, as interactive rebasing edits are done in a temporary file with a
   '.diff' suffix.

Note that this is the first in a series of PRs that lead up to a larger refactoring effort. As each subsequent PR is submitted it will reference the PR that comes before it, creating a chain.

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