...to point to 'https://mustache.github.io/...'

If `global` is used and handlebars is compiled for browser
usage without a Node.js `global` polyfill, handlebars
fails with a `global is undefined` error.

Fixes #1593

First part of reorganizing and cleaning up test-folders.

Second part of reorganizing and cleaning up test-folders.

Third part of reorganizing and cleaning up test-folders.

Also removed it from published files, since the script doesn't seem to be used.

Fourth part of reorganizing and cleaning up test-folders.

Also reorganized npm scripts.

Closes #1696

AMD modules were removed in v5.

Fixes the following error when running integration-tests:
```
npm ERR! code ERESOLVE
npm ERR! ERESOLVE unable to resolve dependency tree
npm ERR!
npm ERR! While resolving: webpack-test@1.0.0
npm ERR! Found: handlebars@5.0.0-alpha.1
npm ERR! node_modules/handlebars
npm ERR!   dev handlebars@"file:../../.." from the root project
npm ERR!
npm ERR! Could not resolve dependency:
npm ERR! peer handlebars@">= 1.3.0 < 5" from handlebars-loader@1.7.1
npm ERR! node_modules/handlebars-loader
npm ERR!   dev handlebars-loader@"^1.7.1" from the root project
npm ERR!
```

Also upgraded to `@definitelytyped/dtslint`.