Corpus Viewer: add numbers to titles when values not unique

[PrimozGodec]

As we talked last time there should be numbers beside the titles Corpus Viewer when the title attribute does not have unique values. Numbers must match between different Corpus Viewers even when selection is made.

Probably it needs to be added to the corpus since when we select just a few documents in a widget we lose values of not selected documents.

[PrimozGodec]

This one is not fixed yet. Maybe my description is not understandable enough. With #481 we just added an option to select the title attribute, but when this attribute has non-unique values there will be no numbers beside in the corpus viewer.

So if we have a title attribute with values:

• a
• a
• b
• c

We want to see something like this in CorpusViewr (in title section):

• a (1)
• a (2)
• b
• c

And then when we select two middle rows and pass them to another Corpus Viewer we should have titles:

• a (2)
• b

This way we know that we selected the second document with the title a. This will need some modifications in the corpus since we need to remember those numbers in the corpus. I can implement this when I will have time.