support also ojdbc6.jar for Java 1.7

in case of Java 1.7 check for both ojdbc7.jar and ojdbc6.jar file in application ./lib directory, in load path and in environment PATH variable
Merge pull request #351 from yahonda/backport_350_to_release14_branch

[backport to release14] support also ojdbc6.jar for Java 1.7