Support params in report queries

Summary:
Prompt for parameters in queries that use them

Quite a small change.  Minor issues exist:
1. When opening in design view, the data source is opened and therefore the parameters are prompted for (twice)

Bug: https://bugs.kde.org/show_bug.cgi?id=379694

Test Plan: Open a report using paramters, ensure they are prompted for, and ensure they are used correctly

Reviewers: staniek

Reviewed By: staniek

Subscribers: Kexi-Devel-list

Tags: #kexi

Differential Revision: https://phabricator.kde.org/D15438