Network Explorer: Add exact match by label

[janezd]

Issue

Fixes #264.

Description of changes

Add match by exact label.

@ajdapretnar, if this works for you, feel free to merge. There will be no tests; this widget is what it is -- largely untested. Adding a new option at the beginning (changing the indices of all options) bothered only a single test. :(

Includes

• Code changes
• Tests
• Documentation

[ajdapretnar]

Ok, let's forgo testing. Do I understand correctly that these selections are not even settings, so no migration is necessary?

[janezd]

Ok, let's forgo testing. Do I understand correctly that these selections are not even settings, so no migration is necessary?

This is an excellent question. mark_mode is not a setting. But mark_hops (used when mode is "Mark nodes in vicinity of selection") is. On the other hand, the text that you enter for "Mark node labeled as" or "Mark nodes whose label starts with" is not even a variable but is read directly from the line edit.

Let us discuss this tomorrow.