ImmutableResultSet check .get_data()

[AlexDo1]

We should check (and test) the get_data() method of class ImmutableResultSet.
Sometimes data is not merged correctly, I'm not sure why that is the case (it seems to work for LUBW and Eddy Covariance data).
Duplicate column names seem to be a problem (data coming from result set test:)

This is the .get_data() method:

metacatalog/metacatalog/util/results.py

Lines 339 to 342 in 5dd8b9b

	def get_data(self, verbose=False, merge=False, **kwargs) -> dict:
	"""
	Return the data as a checksum indexed dict
	"""

get_data() does not always return a dictionary!
The method could also get a harmonize parameter with the same functionality as discussed in #160.

[mmaelicke]

@AlexDo1, did we solve this along the way?