Fix Null Prevalue Values on Export of DataTypes

Exporting a DataType that has a Numeric pre-value that has no value
causes an Exception - added null checking to pre value.value
Fixes: U4-4430 MySql primary key issues
Backports fixes for legacy encoding checks and to not do any db lookups for the new membership providers and also ensures the legacy membership provider doesn't do any db lookups on init.
Merge remote-tracking branch 'origin/6.2.0' into 7.1.0

Conflicts:
	src/Umbraco.Core/Configuration/GlobalSettings.cs
	src/Umbraco.Core/Persistence/Migrations/Initial/DatabaseSchemaResult.cs
	src/Umbraco.Tests/Umbraco.Tests.csproj
	src/Umbraco.Web/Security/Providers/UsersMembershipProvider.cs
	src/umbraco.providers/members/UmbracoMembershipProvider.cs
fixes typo
Merge remote-tracking branch 'origin/6.2.0' into 7.1.0

Conflicts:
	src/Umbraco.Tests/Migrations/AlterMigrationTests.cs
Initial implementation of a new package installation approach based on PR-297. Everything is left internal as we don't know when something like this can be introduced.

Idea is to be able to install a complete package using the PackagingService, so that we eventually can obsolete the old Packager/Installer-code.
Adding a note about the usage of the PackageInstallation class in the PackagingService
oops, fixes some logic with a closing bracket in the wrong place
Merge branch '6.2.0' of https://github.com/umbraco/Umbraco-CMS into 6.2.0
oops, fixes some logic with a closing bracket in the wrong place
Merge remote-tracking branch 'origin/6.2.0' into 7.1.0

Conflicts:
	src/Umbraco.Core/Persistence/Migrations/Upgrades/TargetVersionSixTwoZero/AdditionalIndexesAndKeys.cs
	src/Umbraco.Core/Services/PackagingService.cs
	src/Umbraco.Core/Umbraco.Core.csproj
updates the migration order
Added another property to a migration to specify a minimum current version - needed for specifically targeting a migration 'from' a version.  Finally got mysql upgrading from 6.1 to 7.1 without issue, had to re-order a few things and ensure some migrations don't execute based on the 'from' version.
DoResize(-1,-1) - I don't know why you'd ever want to attempt to resize to -1,-1.

Also removed the else clause as it hides the error until later, now size will be null at the appropriate time.
Pointing to the typical error log folder
Update wording on upgrades
Merge branch '7.1.0' of https://github.com/umbraco/Umbraco-CMS into 7.1.0
fixes unit test
reverts the notion of shema migration - we will run migrations normally as we've been doing, this fixes a couple of unit tests too.