Enhance image type support (#18)

* adds tiff support

* doc update

* adds memory-based =IPixelariumImage= implementation

* add usage example for custom user control

* enhance

* clang-format

fix readme

fix docs

lib/imaging/CMakeLists.txt

@@ -15,6 +15,10 @@ set(IMAGELIBSRC
   impl/PixelariumPng.cpp
   impl/PixelariumCzi.hpp
   impl/PixelariumCzi.cpp
+  impl/PixelariumTiff.hpp
+  impl/PixelariumTiff.cpp
+  impl/PixelariumMem.hpp
+  impl/PixelariumMem.cpp
 )
 
 set(IMAGELIBLIBNAME pixelariumimagelib)