Add site module as dependency to the bootstrap/webfiles module

During the training I ran into the problem that code completion failed in a strange way for items of the type HstSiteMenu in a freemarker template in bootstrap/webfiles. Only half of the properties were autocompleted correctly. Jetbrains confirmed this is indeed a bug and I expect that it will be fixed in an upcoming release. See the issue at https://youtrack.jetbrains.com/issue/IDEA-143177.

The point is that for us things will get worse. At the moment the site module is not a dependency of the bootstrap/webfiles module but somehow code completion works, for example for org.example.beans.NewsDocument you get the correct completion when you have:

<#-- @ftlvariable name="document" type="org.example.beans.NewsDocument" -->

After the fix I suspect that we need the site module as a dependency in the webfiles module to make it all work again.