Migration to ESLint

[nikithauc]

Summary of changes

1. Added eslint rules, picking some rules from https://github.com/microsoft/TypeScript/blob/master/.eslintrc.json.
2. Removed try catches where the catch was simply rethrowing the error.
3. Applied no-inferrable-types. Example - const x:number = 1 will now be const x = 1. The goal of this to avoid redundancy and verbose code.
4. Sorted imports.
5. Replaced options.hasOwnProperty(i) with Object.prototype.hasOwnProperty.call(options, i). https://stackoverflow.com/questions/12017693/why-use-object-prototype-hasownproperty-callmyobj-prop-instead-of-myobj-hasow
6. Additional code improvements with use of variables.

[baywet]

Thanks for making that change. This is greatly going to reduce review workload as well as bring some extra consistency to the code.