Add recognizable prefix string to profiling log statements

This commit simply prefixes the profiling log strings with
the word "PROFILE", so that they are easy to grep for in
the output.
Maint: Fix a markdown glitch in hiera_include doc string

Without a line break, markdown parsers would fail to render the
yaml example as a code block.
Add test for new PROFILE prefix on log messages
Merge pull request #1581 from nfagerlund/hiera_markdown

Maint: Fix a markdown glitch in hiera_include doc string
Merge pull request #1545 from cprice-puppet/maint/master/make-profiling-output-greppable

Add recognizable prefix string to profiling log statements