Models are displayed in Content assist that have been imported by other projects

[aedelmann]

Steps to reproduce:

1. open vorto.eclipse.org/editor
2. Create project
3. Create functionblock model
4. Import datatype from model browser, e.g. mytype
5. Create status property in fb model and open content assist for type

Expected: Only primitive types and project import type 'mytype' is displayed and can be used.
Actual: Other types are shown from other projects or even other users