Autofac 7.0 breaks multitenant support

[lechu445]

After upgrade Autofac to v7.0.0 in project that uses Autofac.Multitenant v6.0.0 errors occur

System.TypeLoadException : Method 'BeginLoadContextLifetimeScope' in type 'Autofac.Multitenant.MultitenantContainer' from assembly 'Autofac.Multitenant, Version=6.0.0.0, Culture=neutral, PublicKeyToken=17863af14b0044da' does not have an implementation.

It looks Autofac.Multitenant 7.0.0 supporting Autofac 7.0.0 needs to be released.

[lechu445]

@alexmg please look at it

[alistairjevans]

I'll sort this out now; should be a simple fix.