Make RecordType enum names more general

**Is your feature request related to a problem? Please describe.**
RecordType is set very specifically, ie.:
```python
class RecordType(Enum):
    f64_matrix = 1
    file = 2
``` 

and since the type is to be exploited more (in ert3) in the near future we might consider rename it for instance: 
```python
class RecordType(Enum):
    numerical = 1
    blob = 2
``` 
