BUG: Use printable type for prints chars

Added helper method to convert char type to integers before
print. This prevents printing of non-printable charaters.

Change-Id: Iea67f87805a81c6a7546236b326f85ea8d3f39dd
Merge topic 'SIMPLEITK-210_UsePrintableTypesInToString' into next

b424825 BUG: Use printable type for prints chars