Import from the domain model interchange format

[kshychko]

Now when we have export functionality aligned, let's do the import now.
We start simple - without the support of sub-resources.
When a file is imported the code should look for a match between resources in the imported file and packages in the StarUML project - the same as it was implemented before.
Tricky moments:

1. DataTypes can be updated with new types, so probably this is the first thing that needs to be checked. If DataTypes package doesn't exist in the root of the project it needs to be created.
2. Relationships in the imported files don't have end1/edn2 properties and can belong to the child class instead of parent one in the StarUML project. Both child and parent classes need to be checked if the relationship exists. If it doesn't exist let's add it the same way as StarUML does - to the child class with the end1 is a child and end2 is a parent. I'll add the rule mapping for aggregation/composition a bit later, but it must be the same as for the import.
3. StatusCode enum. If it doesn't exist in the StarUML project it needs to be added to the root with the values - active/deleted/deprecated/proposed.