Start implementation of database functionality, starting with table generation.

This database will be stored in the user's XDG_DATA_HOME directory under a folder called `com.github.joshstrobl.koto`.

Refactored Koto Track Listing into a dedicated Disc View component, break apart out CDs / Discs into relevant Disc View components, sorting them by the disc and showing a label if there are more than one discs / CDs.

Started using the row-activated event for our Artist GtkListBox instead of having press events on the artist buttons. Makes switching between artists far more reliable. Added a slide left / right stack animation and set its animation to 400ms so it's in the goldilocks zone (IMO) of not being too fast or too slow.

Fix a warning related to scale factor fetching in the PlayerBar.

src/db/db.h

@@ -0,0 +1,22 @@
+/* db.h
+ *
+ * Copyright 2021 Joshua Strobl
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * 	http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <sqlite3.h>
+
+void close_db();
+void open_db();
+