Fixes #10438 - Removed trends:clean task, as it is no longer needed

(cherry picked from commit d933e388953ea5f4b89cb5f0a095251628e0d5cf)

Fixes #7096 - Adds STI to templates

This commit converts Ptables to be just another type of Template so it
gets the same features as ConfigTemplate. ConfigTemplate was renamed to
ProvisioningTemplate to reflect UI and the name under it's commonly known.

fixes #10695 - don't seed initial taxonomies if there are any already

Fixes #10487: Add custom logging support

This change moves away from the Rails logger to the 'logging' gem
to support more configurability of logging. Further, this allows for
the creation of custom loggers that plugins can then create during
registration (with `logger`) or through settings....

Fixes #10439 - add tests for trends:reduce task to deal with additions

Fixes #10402: add to_bool function for converting to boolean.

This commit adds a to_bool function for casting values to boolean
as well as an example usage.

http://projects.theforeman.org/issues/10402

Fixes #5568 - Improves performance of trends:clean rake task

Perform trend counter dupe counting within the database rather than in the Ruby code.

Fixes #8727 - DHCP validation does not fail on discovered leases

fixes #9775 - always load Encryptable when key's missing, log runtime warning

a59972c3 causes Encryptable to be loaded before the encryption_key.rb
initialiser and the majority of the class was skipped as the key was undefined.

Now Encryptable always loads, but logs at runtime if the key is unavailable,...

Fixes #7505 - Changed the way trends are stored in the DB. Now they are stored as intervals