(SUP-2677) Deprecate backup functionality

[elainemccloskey]

If the parameter pe_databases::manage_database_backups is set (to true or false) a notify warning is displayed on Puppet runs about deprecation and removing this param.
This warning doesn't come up if this parameter is not set.

Note added to readme regarding the deprecation.

[puppet-community-rangefinder]

pe_databases is a class

that may have no external impact to Forge modules.

This module is declared in 0 of 578 indexed public Puppetfiles.

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These results were generated with Rangefinder, a tool that helps predict the downstream impact of breaking changes to elements used in Puppet modules. You can run this on the command line to get a full report.

Exact matches are those that we can positively identify via namespace and the declaring modules' metadata. Non-namespaced items, such as Puppet 3.x functions, will always be reported as near matches only.

[jarretlavallee]

LGTM