Add support for searching / and + symbols

[thirdpolice]

Forward slashes and plus signs are ignored in the frontend search, making it impossible to search for, e.g. 'steps:"+1/+0"' and leading to false results such as 'steps:20' returning variants that mention "+2/+0".

EDIT: A better example, to show its importance: we track +1/+1 counters as a standard result, and this makes it difficult to find combos with that output.

[thirdpolice]

The error message is broken too.

[ldeluigi]

Gj