Resources (#1)

* start some resource fiddling

* start some resource fiddling

* initiate a real resource manager

* fix color flicker in rendering

* delete unintended constructors

and add a convenience function to reset the render-image (from the
original image, aka. clone again)

* [OpenGL deprecation warning]

The compiler said that these functions are "deprecated". They seem to
be useless anyway...

* various improvements

* add resource enumerator and documentation

* fix constness stuff

* use existing iterator for insertion

* init unit tests

* rm bogus file

---------

Co-authored-by: m-aXimilian <keuffnermax@gmail.com>

CMakeLists.txt

@@ -57,11 +57,11 @@ add_compile_options("$<$<CXX_COMPILER_ID:MSVC>:/utf-8>")
 
 add_executable(${PROJECT_NAME} ${SRC})
 
-message(STATUS "Linking " pixelariumimagelib)
 target_link_libraries(${PROJECT_NAME}
   PRIVATE pixelariumimagelib
   PRIVATE pixelariumrenderlib
-  PRIVATE pixelariumutilslib)
+  PRIVATE pixelariumutilslib
+  PRIVATE pixelariumresourcelib)
 
 target_include_directories(${PROJECT_NAME}
   PUBLIC ${PROJECT_SOURCE_DIR}/src
@@ -91,3 +91,13 @@ if(APPLE)
     PUBLIC glfw
     PUBLIC "-framework OpenGL")
 endif()
+
+
+option(PIXELARIUM_BUILD_UNITTESTS "Generate Unittests" ON)
+
+
+if(PIXELARIUM_BUILD_UNITTESTS)
+  include(CTest)
+  enable_testing()
+  add_subdirectory(tests)
+endif()