Build tool options rework

[jeffposnick]

R: @philipwalton

This is a general refactor of the directory structure and inheritance for our joi-based options validation. In the process, I loosened one of the restrictions so that developers using workbox-build's generateSW mode could use runtimeCaching could be used without precaching (fixes #2078).

The PR got pretty large, given all the files moved around, so I'm going to submit a follow-up PR that deals with JSDocs for our options, which I think is ultimately a more sustainable documentation setup than what we currently use. (C.f. https://github.com/google/WebFundamentals/tree/master/src/content/en/tools/workbox/_shared/config)

[workbox-pr-bot]

PR-Bot Size Plugin

Changed File Sizes

File	Before	After	Change	GZipped
packages/workbox-build/build/index.js	3.30 KB	613 B	-81%	344 B	🎉
packages/workbox-webpack-plugin/build/generate-sw.js	4.24 KB	4.21 KB	-1%	1.61 KB
packages/workbox-webpack-plugin/build/inject-manifest.js	5.12 KB	5.10 KB	-0%	1.77 KB

New Files

File	Size	GZipped
packages/workbox-build/build/generate-sw.js	1.99 KB	966 B
packages/workbox-build/build/get-manifest.js	1.60 KB	779 B
packages/workbox-build/build/inject-manifest.js	3.13 KB	1.36 KB

All File Sizes

View Table

File	Before	After	Change	GZipped
packages/workbox-background-sync/build/workbox-background-sync.prod.js	3.87 KB	3.87 KB	0%	1.60 KB
packages/workbox-broadcast-update/build/workbox-broadcast-update.prod.js	1.02 KB	1.02 KB	0%	578 B
packages/workbox-build/build/_types.js	41 B	41 B	0%	61 B
packages/workbox-build/build/generate-sw.js		1.99 KB		966 B
packages/workbox-build/build/get-manifest.js		1.60 KB		779 B
packages/workbox-build/build/index.js	3.30 KB	613 B	-81%	344 B	🎉
packages/workbox-build/build/inject-manifest.js		3.13 KB		1.36 KB
packages/workbox-cacheable-response/build/workbox-cacheable-response.prod.js	611 B	611 B	0%	357 B
packages/workbox-cli/build/app.js	4.16 KB	4.16 KB	0%	1.64 KB
packages/workbox-cli/build/bin.js	940 B	940 B	0%	502 B
packages/workbox-core/build/workbox-core.prod.js	5.94 KB	5.94 KB	0%	2.46 KB
packages/workbox-expiration/build/workbox-expiration.prod.js	2.95 KB	2.95 KB	0%	1.27 KB
packages/workbox-google-analytics/build/workbox-offline-ga.prod.js	1.97 KB	1.97 KB	0%	916 B
packages/workbox-navigation-preload/build/workbox-navigation-preload.prod.js	660 B	660 B	0%	323 B
packages/workbox-precaching/build/workbox-precaching.prod.js	4.99 KB	4.99 KB	0%	1.94 KB
packages/workbox-range-requests/build/workbox-range-requests.prod.js	1.58 KB	1.58 KB	0%	801 B
packages/workbox-routing/build/workbox-routing.prod.js	3.09 KB	3.09 KB	0%	1.36 KB
packages/workbox-strategies/build/workbox-strategies.prod.js	4.10 KB	4.10 KB	0%	1.13 KB
packages/workbox-streams/build/workbox-streams.prod.js	1.46 KB	1.46 KB	0%	721 B
packages/workbox-sw/build/workbox-sw.js	1.34 KB	1.34 KB	0%	748 B
packages/workbox-webpack-plugin/build/generate-sw.js	4.24 KB	4.21 KB	-1%	1.61 KB
packages/workbox-webpack-plugin/build/index.js	349 B	349 B	0%	255 B
packages/workbox-webpack-plugin/build/inject-manifest.js	5.12 KB	5.10 KB	-0%	1.77 KB
packages/workbox-window/build/workbox-window.dev.umd.js	40.62 KB	40.62 KB	0%	8.92 KB
packages/workbox-window/build/workbox-window.prod.umd.js	4.48 KB	4.48 KB	0%	1.83 KB

Workbox Aggregate Size Plugin

3.5KB gzip'ed (23% of limit)
7.87KB uncompressed

[coveralls]

Coverage increased (+0.2%) to 79.314% when pulling 8475dbe on options-rework into d7a7cc0 on master.

[philipwalton]

LGTM with one small nit.