tools: FatImageReader added
ibrcommon: Make method in File const and add isRoot() method
tools: dtnoutbox restructured and fixed

Classes ObservedFATFile and ObservedNormalFile removed
ObservedFile pointer changed to objects
Clean-up improved
FAT methods encapsulated into special classes
ibrcommon: Make methods of File virtual and allow subclassing
ibrcommon: Fix handling of '/' file with File class
tools: Moved configuration of dtnoutbox into a class
tools: Removed redundant root checking in FATFile
tools: Fix method overloading in io-utils
tools: Catch failures in dtnoutbox while preparing a bundle to sent
recipes: Disable logging in libtffs for buildroot