jtwig-spring: Add global "beans" object for resolving spring beans by name

Added simple Spring beans resolver to modelmaps which allows doing things like this:
```
<a href="{{ beans.pagination.firstPageUrl(dataTable.page) }}">test</a>
```
We could use some special symbol to referring to beans resolver e.g. @bean or $bean, but both look like invalid twig syntax:
![hvtbrch](https://f.cloud.github.com/assets/20525/2478861/46a145a4-b089-11e3-8740-4b56f836acbd.png)

Let me know what you think about this idea and implementation.