Exception is thrown if trying to run mysql in med trust. Migrations arranged to execute schema migrations first and then data migrations. If a schema migration fails it will attempt to run the downgrade scripts of the migrations if running mysql since schema changes aren't supported in transactions. Updated all sql syntax providers to try to return only the column indexes, not key indexes. Updates the db version checker to include errors for all missing columns, indexes and constraints in the db and vice versa in the schema.
Merge remote-tracking branch 'origin/6.2.0' into 7.1.0

Conflicts:
	src/Umbraco.Core/Persistence/Migrations/Initial/DatabaseSchemaResult.cs
	src/Umbraco.Core/Persistence/Migrations/Upgrades/TargetVersionSixTwoZero/AdditionalIndexesAndKeys.cs
	src/Umbraco.Web.UI/install/Default.aspx.cs
Updates the required migrations to be Schema migrations, ensures the foreign key deletion occurs with the correct supported syntax across db types. Ensures we don't try to drop a pk in mysql when it never existed.