(design) Scan Barcode Component

[jniles]

Our current barcode scanning sits in a couple of controllers .. yet this is an ideal place for component. Furthermore, the current design is limited because you cannot re-focus the hidden input once it has be blurred.

Design Proposal
I propose we design component bhScanBarcode with the following signature:

<bh-scan-barcode on-scan-callback="ParentCtrl.callback(entity)">
</bh-scan-barcode>

The bhScanBarcode component itself would have the logic for re-focusing the input if it got blurred. In pseudocode, this would look like:

var $input = $('[hidden-barcode-input]');
var $button = $('[input-focus-button]');
$input.on('blur', function () {
  $button.show();
});

$button.on('click', function () {
  $input.focus();
});

When a barcode was successfully scanned, it would need to look up the correct value for the barcode using the /barcode route, and then call the on-scan-callback() with the entity as a parameter. The parent controller would then be responsible for doing any other processing.

In this way, the barcode component would be testable and much easier to work with.

[jniles]

Closed in #2630