Bug 24695: Improve SQL report validation

Bug 24695: Improve SQL report validation

The saved SQL report code validates the SQL in multiple places:
when saving, when updating, and when executing the query.
Move the validation code into Koha::Reports, and write tests for it.

Test plan:
1) Apply patch
2) Create a new valid SQL report, save it (success)
3) Create a new illegal SQL report, try to save (fails)
4) Update already saved SQL report by adding one of
   the forbidden words, eg. delete or drop (saving will fail)
5) Edit a save_sql in the database, changing it to eg.
   "drop borrowers", and try to execute it (fails)
6) Prove t/db_dependent/Koha/Reports.t

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Work as described, no qa errors.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Bug 24695: (QA follow-up) Fix number of tests

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>