0023348: Expression 'ii >= 0' is always true. Unsigned type value is always >= 0.

0023348: Expression 'ii >= 0' is always true. Unsigned type value is always >= 0.

Redesigned the loop to work correctly with unsigned variables.
Treatment of path to source file is rewritten using OSD_Path for more clarity
Command getsourcefile corrected to return its result as Tcl string, and simplified
Error in treatment of optional arguments in substituted puts is fixed in src/DrawResources/TestCommands.tcl
Test case added: demo draw getsource