286/migrate to eslint add prettier

[saifahn]

Adds ESLint, removes TSLint file.

There are a number of new dependencies:

• @typescript-eslint/eslint-plugin allows typescript specific rules to be used in eslint
• @typescript-eslint/parser allows eslint to parse typescript correctly
• eslint-config-prettier turns off rules that would conflict with prettier
• eslint-plugin-prettier allows eslint and prettier to be run in one command -> prettier is run as part of eslint

Each of these have their own dependencies (1-4 of them). Is this acceptable?

Additionally, I added comments in the .eslintrc.js as notes as to what each rule does, should these remain?

[saifahn]

The latest commit is a big one as it formats all the code according to prettier.