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

examples/simple/simple.cpp

@@ -1,9 +1,9 @@
 #include <memory>
 
 #include "DefaultApp.hpp"
-#include "resources/resource.hpp"
-#include "utilities/ILog.hpp"
-#include "utilities/SpdLogger.hpp"
+#include "ILog.hpp"
+#include "SpdLogger.hpp"
+#include "resource.hpp"
 
 using namespace pixelarium;
 using namespace std;
@@ -12,23 +12,22 @@ using Pool = resources::ImageResourcePool;
 
 // setup a logger
 #ifdef _WIN32
-unique_ptr<Log> logger{
-    make_unique<utils::log::SpdLogger>(string(getenv("APPDATA")) + "/pixelarium/simple_app.log", "default")};
+const auto logger{utils::log::SpdLogger(string(getenv("APPDATA")) + "/pixelarium/simple_app.log", "default")};
 #else
-unique_ptr<Log> logger{
-    make_unique<utils::log::SpdLogger>(string(getenv("HOME")) + "/.cache/pixelarium/simple_app.log", "default")};
+const auto logger{
+    utils::log::SpdLogger(string(getenv("HOME")) + "/.cache/pixelarium/simple_app.log", "default")};
 #endif
 
 int main()
 {
     // some initial log message and default log level setting
-    logger->Info(format("{}: Starting Application {}", __FUNCTION__, "Pixelarium"));
-    logger->ChangeLevel(utils::log::LogLevel::kDebug);
+    logger.Info(format("{}: Starting Application {}", __FUNCTION__, "Pixelarium"));
+    logger.ChangeLevel(utils::log::LogLevel::kDebug);
 
     // instantiate an image pool for the application
     resources::ImageResourcePool image_pool;
 
     // create an application, inject its dependencies and start it
-    auto app{application::DefaultApp(*logger, image_pool)};
+    auto app{application::DefaultApp(logger, image_pool)};
     app.Start();
 }