Upgrade projects

Now using
- gradle wrapper v6.0
- androidx
- stable android gradle plugin v3.5.0
- target and compile sdk set to 29

expense_planner/.idea/vcs.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="$PROJECT_DIR$/.." vcs="Git" />
+  </component>
+</project>