Add a clarification in packageTemplateEnv

Improve the pre-processing message so we can see which unit is being
built, not just the source component name.

Debug output while building to print out the installed package info
when we register information.

Remove a done TODO about making sure the installed package registration
files do not clash with each other, by including the full UnitId. This
did not need any code changes here since dislaying the UnitId does the
right thing.