In dev mode this means changes to ts files can now be watched
live.

Can now build all with 'gulp' (if gulp-cli installed)

Big commit. Breakdown:
 - .gitignore includes gulpfile.js (otehrwise excluded)
 - gulpfile sets up build steps + browsersync
 - src/ files for FE (stub for now)
 - moved ts to src/ for consistency
 - update tsconfig with new paths
 - package.json lists new reqs