add support for scpecial characters

Add support for special characters on search.

Example: When I search for "Sao Paulo" (without ~) doesn't match with "São Paulo" (with ~).

I added a function convert_accented_characters, it convert a search query and search results special characters to match.
I desagree about `get_search_text`. But the conversion needs to happen before escaping.

I will fix this in my next commit.