add tooltip to cells if 'truncate' variable is set

If a Column has the 'truncate' variable defined, we should
have a tooltip to show the full text if user hovers over
a cell. For example, Project > Volumes Description column is
truncated at 40 chars. 'Truncate' column attribute should be
used on Strings, not Integers, fixed test case.

Change-Id: I960744f73b84e54d196e264039ebba9614db372b
Closes-Bug: #1369944
Merge "add tooltip to cells if 'truncate' variable is set"