Allow expressions in text attributes

[ChrisMBarr]

We use a translation filter to display our UI in multiple cultures, so we have to use expressions instead of plain text in many situations. This PR allows the traditional use of these attributes, as well as the following:

<table class="table table-bordered"
       ts-wrapper
       ts-item-name="page.ITEM_NAME_SINGULAR' | translate"
       ts-item-name-plural="'page.ITEM_NAME_PLURAL' | translate"
       ts-no-data-text="'page.NO_PAYMENTS_MATCH_CRITERIA_MESSAGE' | translate">

[mattiash]

Code looks good, but could you update Readme.md to include documentation for the feature as well?

[ChrisMBarr]

@mattiash ok, done