feat(engine/VarInstQuery): handling of binary & serializable types

Binary:
- enable query for binary variabes
- value will not be fetched by default
- value will be fetched if .fetchBinaryValues(); is called

Serializable
- Query will attempt to de-serialize values
- if de-serialization fails, the query will not throw an exception but
provide an error message on the failed variable instance.
feat(engine-rest): variable instance resource

Add new resource:

GET /variable-instance/{id}
	returns the default Json representation

GET /variable-instance/{id}/data
	returns the binary content of a binary variable

related to #CAM-2007
feat(rest): MessageBodyReader for MultipartForm Data

custom JAX-RS @Provider: MessageBodyReader for MultipartForm Data.

related to #CAM-2010
feat(Rest): POST for binary variables

POST the content of a binary variable:

	POST /execution/{id}/localVariables/{varId}/data
	POST /process-instance/{id}/variables/{varId}/data

Content type is multipart/form-data
Parts:
* data: the data. Content type is either
    * octet-stream => handling as byte array
    * application/json => handling as serializable, "type" is required
* type: only for type Serializable: the java type of the json serialized
data

related to #CAM-2011
feat(rest): type for serializable
feat(cockpit): support for binary variables

- Byte array variables can be downloaded and uploaded.
- Serializable variables can be edited as Json Object Representation.

related to #CAM-1419