PATCH - No longer MySQL specific

[sensei-hacker]

This fixes some MySQL-specific and erroneous quoting, so it now runs on other RDMS systems such as Microsoft SQL Server. More specifically:

Bound parameters are not quoted, as the binding handles that (uses ?, not "?").

String literals use single quotes, double quotes are for identifiers (MySQL accepts backticks for identifiers): http://www.savage.net.au/SQL/sql-2003-2.bnf.html#character%20string%20literal

Use Moodle's $DB->sql_concat rather than MySQL-specific CONCAT()

https://github.com/MorrisR2/moodle-block_quickfindlist/commit/e708c8063ba7e5941233834afcb4f06949bc0f4c

[sensei-hacker]

Closed as part of #13 batch "update for Moodle 2.7"