play: javascript code in play.html should be moved to a .js file

[Trek Hopton]

Javascript code in play.html should be moved to a .js file because the functions are growing in size and the file is getting harder to read and expand on. Also javascript editor tools can then recognise and work with the code.

Everything in the script tag can be moved to a new file: play.js.

[Trek Hopton]

Relsolved in PR #49