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

generate_coverage.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+
+SCRIPT_PATH="$( cd -- "$(dirname "$0")" >/dev/null 2>&1 ; pwd -P )"
+HTML_COV_PATH="coverageReport/html"
+HTML_START_FILE="index.html"
+
+echo "Generating Coverage report for ptouch-prnt"
+
+ninja -C builddir
+ninja -C builddir test
+
+mkdir -p ${HTML_COV_PATH}
+gcovr --html --html-details --html-syntax-highlighting --filter src --output ${HTML_COV_PATH}/${HTML_START_FILE}
+
+if [ $? ] 
+then
+  echo "Coverage report successful generated!"
+  echo "Open: file://${SCRIPT_PATH}/${HTML_COV_PATH}/${HTML_START_FILE}"
+else
+  echo "Error generating coverage report!"
+fi