Several document versions

Now dispatcher can make use of different versions of the servioticy data model. It needs that the documents specify the version, or it will assume it is the default one.
The current versions are:
 - 0.1.0 (default)
    Works with JSONPath. Each computation is only one JS assignment. Has pre-filters and post-filters.
 - 0.2.0
    Each computations is a Javascript function, which its parameters declaration define the inputs. The filtering is done by returning a type different than the one defined (the easy way is returning null).