Improve search function in unicode plugin

The ``~emoji(a) emoji`` command now only looks for matching characters in the following blocks : Emoticons, Misc_Pictographs, Transport_And_Map, Misc_Symbols and Dingbats. This should filter out most of the irrelevant characters when searching for an emoji. The ``unicode ~query(a)`` works the same as before.

I also added a bit of fuzziness server side, this should make finding characters easier.