Stop using the WiX src attribute

Stop using the WiX src attribute

The src attribute has been deprecated for a while in favor of
different (more descriptive) attributes for the different XML
elements involved.

For the File element, use the Source attribute.
For the Directory element, use the FileSource attribute.
For the Merge, Binary, and Text elements, use the SourceFile attribute.

This makes the installer build much quieter, with the warnings from
the light.exe invocation all fitting into the default history buffer.

ticket: 8208 (new)
queue: kfw
tags: pullup
target_version: 1.13.3