Get rid of PHP to communicate with the database during designtime

[hanjoosten]

As has been shown in issue #557 , --validate causes problems when there are enough violations in a single rule. These problems are due to the fact that we have php as an intermediate way to run SQL queries.

PHP is only used to build and querie a temporary database in the case of --validate. Other uses of PHP are already replaced by using JSON.

There are several database interfaces possible. We have to remind, that we want to prove that the SQL that we generate (and hand over using JSON) is correct. Therefore, HaskellDB is probably NOT suitable, for it abstracts away from SQL. (Very cool, by the way). Currently, at first sight I think that mysql-simple might be the right choice for this single requirement. It doesn't contain a way to construct queries, but we allready do that using simple-sql-parser.