Add a package-shared-dependencies that pulls in webfiles

The repository cannot include webfiles. This is because webfiles depend on the repository api. Instead, we need to provide webfiles via a package dependency. We already have:

http://svn.onehippo.org/repos/hippo/hippo-cms7/packages/trunk/

In there, we have

package-app-dependencies/
package-cms-dependencies/

both of these packages need to have webfiles dependency: Namely the app dependency is meant for SITE + REPO and cms dependency is meant to be used for CMS + REPO. Hence, we'll create a third dependency pom:

package-shared-dependencies

in their, we'll add a pom dependency that pulls in webfiles. Both package-app-dependencies and package-cms-dependencies will include package-shared-dependencies.

We'll update documentation in http://www.onehippo.org/library/enterprise/installation-and-configuration/separate-hst-deployment-model.html