Add schema version to kproj files
Refactoring IFileSystem

Making AssemblyNeutral and creating .Interfaces package
Changing semantics of string property to be relative
Updating tests
Changing return value to be always non-null with Exists property
Refactoring IFileSystem

1. Addressing some code review comments
2. Removing net45 target for file system packages as net45 target is not being used by any component.
3. Adding a method on IFileInfo interface to retrieve a file trigger. Implementation is not done yet.
Fixing the test project with changes
Addressing Pranav's CR comments
PR comments

1. Changed to IExpirationTrigger
2. Fixed some doc comments
3. Removed .Interfaces from the namespace.
4. Allowing a leading slash for relative file paths or directory paths.
Addressing PR feedback

Adding a test for verifying WriteContent and Delete file scenarios.
Some more changes

Razor requires the file system built for net45. So bringing back net45 target
Not returning NotFound on empty directory name values.

This is a regression in behavior which broke an MVC test.
Some more PR feedback
Adding more tests
Some more PR feedback