Enforce unique Rules (Old Urls)

[m-jedynak]

Now it's possible to add duplicated rules both manually and automatically

I think that we should have unique entries based on (OldPattern, RedirectRuleType, IsActive)

Consider 3 cases:
a) when "System" rule is added then overwrite previous redirect rule
b) when new Manual rule is added either ask user what to do (more complex) or ask user to remove duplicate first (simpler)
c) when importing from CSV add an option to either overwrite or skip duplicated rules