targetPointer ITS attribute not correctly supported in XML/ITS filter

[Martn Wunderl]

Currently, the target pointer feature in the filter is not completely implemented. The following would need to be added:

• create a non-existing target element, if not existing, yet
• place existing target text in the TU’s target
• add 100% match for existing target
• on merge, add translated texts back into the target element
• as a bonus of lower priority: ability to group elements (might not be supported by ITS)

[YvesS]

I've merged PR 128 since it improves greatly the Target Pointer feature. We still have open issues:

• Target element has to be after the source
• Target element/attribute have to exist (empty)
• We do not support element with inline codes (I've added a unit test for that: https://bitbucket.org/okapiframework/okapi/commits/dev#Lokapi/filters/its/src/test/java/net/sf/okapi/filters/xml/XMLFilterTest.javaT912)