Add simple calendar application (#38)

* cal: initial version

* cal: hacks to get more functionality working

* cal: Disable file output for now

* cal: Got button mapping to work

* cal: tweak power and size

* cal: Tweak layouts

* cal: got events to display

* cal: single day addition now works

* cal: got file i/o to work

* cal: Layout tweaks

* cal: Tweak add dialog

* calendar/columns: start separate apps for them

* calendar: open keyboard

* calendar: make keyboard fit on small screen

* calendar: better metadata for calendar

* calendar: more metadata tweaks

* calendar: revert hello tweaks

* calendar: revert columns changes.

* calendar: remove manifest from columns

* calendar: attempt to fix MANIFEST

internal_filesystem/apps/cz.ucw.pavel.calendar/META-INF/MANIFEST.JSON

@@ -0,0 +1,24 @@
+{
+"name": "Calendar",
+"publisher": "micropythonos",
+"short_description": "Calendar",
+"long_description": "Simple calendar app.",
+"icon_url": "https://apps.micropythonos.com/apps/cz.ucw.pavel.columns/icons/cz.ucw.pavel.columns_0.0.1_64x64.png",
+"download_url": "https://apps.micropythonos.com/apps/cz.ucw.pavel.columns/mpks/cz.ucw.pavel.columns_0.0.1.mpk",
+"fullname": "cz.ucw.pavel.columns",
+"version": "0.0.1",
+"category": "utilities",
+"activities": [
+    {
+      "entrypoint": "assets/main.py",
+      "classname": "Main",
+      "intent_filters": [
+        {
+          "action": "main",
+          "category": "utilities"
+        }
+      ]
+    }
+  ]
+}
+