Review npm dependencies used/shipped

[DonJayamanne]

Some of the following are either not used or used only in the DS UI (hence must be moved to devDependencies)

• "@blueprintjs/select": "3.10.0", - not used
• less-plugin-inline-urls - not used
• memoize-one - used in DS
• Plenty more Check others.

This increases the over all size of the extension, hence the load times/perf of the extension.
We should:

• Identify items no longer used & remove
• Move DS UI specific items into devDependencies
• Identify what is used for development (but found in dependencies) and move them into devDependencies

[IanMatthewHuff]

There is a chance that this could get longer if we are doing things like trying to replace large packages with smaller ones. But for just a scrub and moving stuff to dev it seems like this shouldn't be too bad.

[IanMatthewHuff]

Validated.