Fix for manual targeting of Thor not working against emp immune units, issue #4207

[emb3rn]

Work done

Hi, this is my first PR/contribution so let me know if there are any issues.

Decided to look into and fix #4207 since it's been there since January and seemed like a good start.

luarules/gadgets/unit_onlytargetcategory.lua
Previously didn't correctly implement a break statement, which meant that the target categories for Thor (and possibly other units) weren't disregarded if there were multiple categories, which is the intended behaviour according to the original comment:

elseif unitOnlyTargetsCategory[udid] ~= category then -- multiple different onlytargetcategory used: disregard

Also removed a random incrementing i = i + 1 which didn't do anything lol

luarules/gadgets/unit_onlytargetempable.lua
Changed the code to only consider a unit to be an "emp unit" if all of it's weapons have a paralyze effect, which sounds logical to me. If a unit has weapons that don't emp/paralyze, then the player should be able to target emp immune enemies as they have normal non emp weapons. The emp weapons will not fire anyway as those are handled elsewhere.

Screenshots:

boom.mp4

com goes boom (with manual click, you can see hold fire is enabled)

[emb3rn]

Looks good to me, let me know if there are any needed changes