Fix Logger and other build issues (#7)

This branch fixes a couple of issues with the build
- stop linking everything in a library which is then linked against a single main. It doesn't work the way I wanted. If functionality needs to be exposed by a library, it can be done later or with a separate target
- This should also fix spdlog
- Source files are now in a separate meson file using mesons files() feautre
- Improve coverage generation by adding a script generating html coverage reports. This will hopefully keep the motivation higher to create more unit tests
- Increase the code coverage a bit to demonstrate that statement above is not a fluke 😄

Reviewed-on: #7

tests/meson.build

@@ -1,6 +1,6 @@
-tests = [['bitmap_test', 'bitmap_test_exe', ['bitmap_test/bitmap_test.cpp']],
-         ['image_test', 'image_test_exe', ['image_test/image_test.cpp']],
-         ['monochrome_test', 'monochrome_test_exe', ['monochrome_test/monochrome_test.cpp']]
+tests = [['bitmap_test', 'bitmap_test_exe', ptprnt_srcs + ['bitmap_test/bitmap_test.cpp']],
+         ['image_test', 'image_test_exe', ptprnt_srcs +['image_test/image_test.cpp']],
+         ['monochrome_test', 'monochrome_test_exe', ptprnt_srcs +['monochrome_test/monochrome_test.cpp']]
         ]
 
 foreach test : tests
@@ -8,8 +8,7 @@ foreach test : tests
          executable(test.get(1),
                     sources: test.get(2),
                     include_directories: incdir,
-                    link_with:[ptprnt_lib],
-                    dependencies: [gtest_dep, pangocairo_dep]
+                    dependencies: [gtest_dep, usb_dep, log_dep, pangocairo_dep, cli11_dep]
          )
     )
 endforeach