Resolve "PDF export for timetables"

Closes #51 (closed)

aleksis/apps/chronos/static/css/chronos/timetable_print.css

+.timetable-plan .row, .timetable-plan .col {
+    display: flex;
+    padding: 0rem;
+}
+
+.timetable-plan .row {
+    margin-bottom: 0rem;
+}
+
+.lesson-card, .timetable-title-card {
+    margin: 0;
+    display: flex;
+    flex-grow: 1;
+    min-height: 40px;
+    box-shadow: none;
+    border: 1px solid black;
+    margin-right: -1px;
+    margin-top: -1px;
+    border-radius: 0px;
+    font-size: 11px;
+}
+.lesson-card .card-content > div {
+    padding: 1px;
+}
+
+.card .card-title {
+    font-size: 18px;
+}
+
+.timetable-title-card .card-content {
+    padding: 7px;
+}