Misc (#19)

* get image returns optional<Mat> instead of unique_ptr<Mat>

* introduce complexity

* rename image load function

* add example for a basic reader for binary image files

* fix windows build?

* add a status bar underneath the menu bar

* use status bar in custom_0 example app

* clang formats

* packing w/ pragma push

* add "Save As" functions to image views

* resize over reserve

* rm local override uri

* add simple thread pool

* rename to simple_thread_pool

* get rid of useless renderlib

* document version inc

* extract hardcoded values to in-header

* clang format patch

* clone registered image in custom_0

* document binary-file header

* minor fixes

* clang format

* rm unused render cmake

lib/app/app_resources_default.h.in

@@ -17,6 +17,9 @@
 #define LOADIMAGE           "Load Image"
 #define REMOVEIMAGE         "Remove Image"
 #define CLEARALL            "Clear All"
+#define SAVEAS              "Save As..."
 // clang-format on
 
 inline constexpr std::array<std::string_view, 5> LOGLEVELS = {"Trace", "Debug", "Info", "Warning", "Error"};
+
+inline constexpr auto kInitialWindowWidth {700.0f};