minor fixes to plugin dev quickstart guide
Revert "minor edit: moving out some text to separate variables for better readability / easier editing"

This reverts commit 30999751be40acac20b9a2d4e401d613f06f4d34.

I did not notice that the dictionary holding the license comparison object was
keyed by resource (file). Thus, moving strings from the dictionary out into
variables is impossible (unless the dictionary will only ever have key, which
is not the case!).
fix quickstart plugin dev guide to conform to reverted changes to test_provider_skeleton module + a few cosmetic changes to the same quickstart guide