Fix parsing of one-to-one metadata

[marcellevstek]

No description provided.

[mstajdohar]

@marcellevstek Rebase, write change log entry, update docs (if needed).

[marcellevstek]

@gregorjerse this PR addresses the issue when a one-to-one metadata table object includes samples that are either not present in the collection or don't have a required data object of certain process type (e.g. MultiQC).

Previously the code failed, which posed an issue if some samples imported from GEO failed to process and we wanted to remove them from the collection. When you import through GEO, a one-to-one metadata table is created for each of the imported samples.

Here is some testing code. Try it with this branch versus the master branch to see the difference.

import resdk
from resdk.tables import QCTables

res = resdk.Resolwe(url="https://app.genialis.com")
res.login()

collection = res.collection.get("test_metadata")
qt = QCTables(collection=collection)

print(qt.meta)