Added OpenRead and OpenWrite methods to IMvxFileStore. Implemented in MvxBaseFileStore, but there are more implmentations to be done.
Needs further review: Implementations of IMvxFileStore for WindowsPhone and WindowsStore - WindowsPhone implementation actually commented out.
Add null check in MvxBaseFileStore.WriteFileCommon.
Fixed calls to "this" in static methods. Changed 2 private static methods to instance methods.
Merge branch 'ExtendFilePlugin' of github.com:Blewzman/MvvmCross into v3.1
Modifications to unify delete behaviour for FileStream read/write - a bit scared of these changes...
Minor fixes to unify file experience - minimize risk of change (sorry!)
Minor fixes to unify file experience - minimize risk of change (sorry!)
Minor fixes to unify file experience - minimize risk of change (sorry!)
Minor fixes to unify file experience - minimize risk of change (sorry!)