restrict new tag entropy

right now, tag one can create tag "sants" even if tag "Sants" already exists. Also, one can create tag "Gràcia " with a final space, that is different from "Gràcia" (without the space). Same thing with non ascii characters: I can tag a new event with "Gracia" even though tag "Gràcia" exists.

This last one is more complicated because in theory there could be different words that only differ in some special mark. But at least in catalan it won't be common. Maybe when mixing languages in tags it's important not to be forced to use another language. But again, even catalan and spanish mixed I can't find any example.

The idea is: the new tag suggestion floating panel, make it suggest:

• lax-matching existing tags (uppercase/downcase, accents)
• blankspace trimmed/stripped string

For our instance this issue is relevant because tag disparity hinders the experience when filtering or searching.