build system and module refactoring + simple histogram scratch (#20)

* scratch adding histogram to image views

Histograms should come from some sort of histogram service. This is
currently just a POC.

* custom logger implementation w/o spdlog

* missing cmake file

* fix tests

* use operator<< over direct stream exposure

* rm print header

* add threading test + refactor towards interface libraries

omits the need for =target_include_directories= calls /everywhere/

* rm print header

* rm constexpr

* templated thread_pool

* fix doxyfile

* default enable doc building

* czi reader refactor

* rm erroneous include expression

* clang-format

* single lib include with PUBLIC visibility

* compile imgui stdlib

* clang format

* documentation update

centralize `LogLevelToString` to `ILog.hpp`

update docs and examples

lib/app/include/DefaultApp.hpp

@@ -0,0 +1,42 @@
+#pragma once
+
+#include <cstddef>
+
+#include "AppGLFW.hpp"
+#include "ILog.hpp"
+#include "PixelariumGallery.hpp"
+#include "imgui_proxy.hpp"
+#include "resource.hpp"
+
+namespace pixelarium::application
+{
+/// @brief Default implementation of AppGLFW.
+/// This can either be used as is, as an example or as a base class
+/// providing some defaults for a more custom implementation.
+class DefaultApp : public AppGLFW
+{
+   public:
+    DefaultApp(const utils::log::ILog& log, pixelarium::resources::ImageResourcePool& pool)
+        : application::AppGLFW(log), pool_(pool), gallery_(log, pool)
+    {
+        gallery_.SetLoadFunction([&]() -> void { this->LoadImageDialogue(); });
+    }
+
+   protected:
+    void MenuBarOptionsColumn1() override;
+    void MenuBarOptionsColumn2() override;
+    void Run() override;
+
+   protected:
+    resources::ImageResourcePool& pool_;
+    application::PixelariumImageGallery gallery_;
+
+   protected:
+    void LoadImageDialogue();
+
+   private:
+    bool image_listp_{true};
+    bool demop_{false};
+    ImVec2 curr_dim_;
+};
+}  // namespace pixelarium::application