Remove entry selection from this group" removes entries from similarly named groups

[luizphilipe2]

JabRef 3.7
windows 10 10.0 amd64
Java 1.8.0_111

Steps to reproduce:

1. Create a Bibtex file with the groups "mygroup" and "mygroup_alternative". Assign a few entries to both of the groups.
2. Select the entries in "mygroup" and remove them from the group using "Remove entry selection from this group".
3. The entries have been removed from both "mygroup" and "mygroup_alternative". Indeed, if you check the group assignments of the entries they now contain "_alternative" as group assignment, i. e., the first part of the group name has been deleted. As no group "_alternative" exists, the items appear to not be assigned to any group.

Note that this bug is related to a workaround/solution to the issue of group hierarchy in JabRef:
#1495

If someone was to use

Asthma
Asthma treatment
Asthma diagnosis

as proposed in #1495, I suspect that the same problem would arise (?).

[luizphilipe2]

discussion #1495

When moving from JabRef 9.10 to 3.4, the philosophy governing groups changed. Rather than
a key being linked to a group in "jabref-meta: groupstree" the group is attached to the individual entry, as in "groups = {culture},",

The big disadvantage is that groups are no longer in a hierarchy but a independent. As the result, a key associated, say, with "culture", is associated with that term everywhere it appears in the database. So when I select "culture", hundreds of keys are elected that use the word "culture" in a different context or meaning. If I understand the situation there is no way now to avoid the hundreds of irrelevant links.

The issue is now to avoid duplicating the situation in the future. I find that if a BibEntries share a
string, they are viewed as the same. Since they are case sensitive, I can distinguish Culture, cUlture, cuLture, etc. Then go through all the keys selected by "culture" and re-associate them with one of the new names. Since this is hundreds of hours of work, I wonder if there is a better method.