- also rename files and directories with "GlobalImport" in name
- nearly blind but avoid "ViewImportss" in new names
- public API change: `ViewHierarchyUtility.GetGlobalImportLocations()` -> `GetViewImportsLocations()`
- primary source updates were comments, tests, and implementation details
nit:
- rename NestedGlobalImports.cs file to NestedViewImportsController.cs, matching class
expire files in razor file cache.
Add a functional test to ensure the compiler cache does not get
initialized until the first request to a View.
Fixes#1708