Framework: Introduce custom ESLint rules, including Lodash import restrictions

[aduth]

This pull request seeks to include the newly published eslint-plugin-wpcalypso package in introducing custom ESLint rules to the Calypso project. Currently, the plugin only contains a single rule: no-lodash-import. This rule intends to prevent an undesirable increase in bundle size as a consequence of importing modules from the root Lodash package, which has been fixed once before in #735. New ESLint rules can be added to the eslint-plugin-wpcalypso package as needs arise.

Testing instructions:

Ensure that Lodash replacements are valid.

Verify that make lint passes (reflected by CircleCI tests passing).

Test that introducing an import from the root Lodash package results in an ESLint error:

1. Edit any file to include import { compose } from 'lodash';
2. Save the file
3. Run ./node_modules/.bin/eslint [filename] in your Terminal
4. Note that the file fails linting with the appropriate error message

Depending on how you use ESLint in your development workflow, you may need to install the eslint-plugin-wpcalypso package globally (using the -g flag). This will be the case if you have installed the base eslint package globally.

[gwwar]

👍 Tested that Calypso runs normally, that warnings appear, and that you're prevented from committing changes with a root lodash import. We may want to update the error message to explain that this is restricted to help reduce bundle size.

Feel free to 🚢 after a rebase.

[aduth]

We may want to update the error message to explain that this is restricted to help reduce bundle size.

I dunno, I kinda like the brevity of ESLint's built-in rules, and tried to adopt a similar feel to the message, in that the text itself should briefly describe what is incorrect, and the rule key should lead you to a more thorough explanation of why it's incorrect.

Per recent discussions, we should also separately consider whether it makes sense to bring the eslint-plugin-wpcalypso into the Calypso repository itself (treating Calypso as a mono-repo, see #2247).