Fix the issue with the LazyItemEnumerable where IsLazy=False remains laz..

Hi Mike,

can you pull this fix into the main branch? This fixes the reported issue https://github.com/mikeedwards83/Glass.Mapper/issues/79

Fix the issue with the LazyItemEnumerable where IsLazy=False remains lazy. Items that are decorated with the SitecoreChildren or SitecoreQuery - Attribute classes with the option to disable the lazy loading is fixed by this.

A side effect of the lazy behavior was that the child items where retrieved in an other UserContext (security scope) than the one where the root object was created in.