Added whitelist for storing options in attributes

Adds the ability to attributes directly instead of using the ui-select2="{}" for setting select specific options.

ex:
```html
<fieldset data-ng-repeat="comp in complications">
    <select ui-select2
                width='100%'
                minimum-results-for-search='-1'
                data-placeholder='Chose an option'
                data-ng-model="select[$index]"
                data-disabled="{{ !selects[comp.spec_field] }}"
                data-ng-change="calculateSelects($index)">
            <option value=""></option>
            <option ng-repeat="(_, spec) in selects[comp.spec_field]" value="{{ spec.guids }}">{{ spec.title.join(', ') }}</option>
    </select>
</fieldset>
```