Use JSDOC documentation for modules

[gfwilliams]

Since updating build.js, we can now do:

Reference
--------------

* APPEND_JSDOC: modulename.js

and can then add simple documentation to each module in the form of:

/** My description
 second line if we want it */
FooBar.prototype.hello = function() {
}

/** Another */
exports.woot = function() {
}

See devices/NRF24L01P.js as an example. We now just need to bash through all the modules and do this.

Note that it doesn't cope with defining functions inside an export.connect function. Ideas for how to sort that appreciated - but for now it can just be documented in a comment above.

[gfwilliams]

If anyone notices a module that could use this and feels like updating it, it'd really be appreciated.