Fix for the Explain issue for mysql before v5.6.3

An attempt is made to determine the mysql version and if it is before 5.6.3, the check against SELECT-only request is performed.
Merge pull request #157 from olegabr/bug-128

Fix for the Explain issue for mysql before v5.6.3
Merge branch 'bug-128' of https://github.com/qcubed/framework