(PE-962) Add schema for flagging latest report per node

This commit adds a new table for storing data about which
report was the most recent for each node.  This will make
it easier to write event queries that only return events
from the last puppet run for each node.

The migration code also has to populate this new table for
all of the existing data.  The commit includes tests
to validate that migration code.
(PE-962) Update latest report for node when storing reports

Prior to this commit, we had the new schema and migration
code for flagging the latest report for each node, but
we weren't updating that data when new reports came in.

This commit adds the code to do those updates every time
a new report is stored, and tests to verify that this
behavior works as expected.
(PE-962) Clean up SQL for initial `latest_reports` population
(PE-962) remove unnecessary extra index on primary key

Because the `node` column of the new `latest_reports` table is already marked as the `PRIMARY KEY`, we don't need to explicitly create an index on it.
(PE-1205) Add support for querying reports by hash

Prior to this commit, we only supported querying for reports
by the certname of the node that the report was received from.
This commit adds support for querying by the report hash,
which can be retrieved from events via the events query
endpoint.
Fix missing paren in doc
Merge pull request #595 from cprice404/feature/burgundy/PE-962-save-last-run-info

Feature/burgundy/pe 962 save last run info
Merge pull request #613 from cprice404/feature/burgundy/PE-1205_query_for_report_by_hash

Feature/burgundy/pe 1205 query for report by hash
(PE-948) Store containment path and class
(PE-949) Store transaction uuid
Updated documentation
Updated tests to right format, use dashes, & test for nils
Pull file/line inclusion out of conditionals, prefer dashes to underscores, little cleanup
Fix test to use dashes instead of underscores
Succinct-ness
Anonymize transaction-uuid in full profile only
Anonymize references in the containment-path