Create new ApplicationSetting for Cloud License

What does this MR do?

This MR adds the columns cloud_license_enabled to the ApplicationSettings table. It will be used later to determine whether self hosted instance would enable the Cloud License feature.

Database log

Up

== 20201117054609 AddCloudLicenseEnabledToSettings: reverting =================
-- remove_column(:application_settings, :cloud_license_enabled, :boolean, {:null=>false, :default=>false})
   (0.2ms)  BEGIN
   (2.3ms)  ALTER TABLE "application_settings" DROP COLUMN "cloud_license_enabled"
   -> 0.0029s
== 20201117054609 AddCloudLicenseEnabledToSettings: reverted (0.0065s) ========

Down

== 20201117054609 AddCloudLicenseEnabledToSettings: migrating =================
-- add_column(:application_settings, :cloud_license_enabled, :boolean, {:null=>false, :default=>false})
   (0.1ms)  BEGIN
   (7.4ms)  ALTER TABLE "application_settings" ADD "cloud_license_enabled" boolean DEFAULT FALSE NOT NULL
   -> 0.0084s
== 20201117054609 AddCloudLicenseEnabledToSettings: migrated (0.0085s) ========

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• [-] Separation of EE specific content

Availability and Testing

• [-] Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Related to #273011