Squashed commit of the following:

commit 22b807c
Author: Arno Welzel <github@arnowelzel.de>
Date:   Wed Jan 16 18:45:52 2019 +0100

    Clarify how to use the occ command

commit 9126804
Author: Arno Welzel <github@arnowelzel.de>
Date:   Wed Jan 16 11:44:10 2019 +0100

    Update README.md

    Updated explanation how to add the custom MIME type for Keeweb.

commit 6e7ac94
Author: Arno Welzel <github@arnowelzel.de>
Date:   Tue Jan 15 18:57:13 2019 +0100

    Updated instructions for mimetype registration.

commit dabab4a
Author: Arno Welzel <github@arnowelzel.de>
Date:   Tue Jan 15 15:48:25 2019 +0100

    Adjust maximum supported version.

commit aafe929
Author: Arno Welzel <github@arnowelzel.de>
Date:   Sat Dec 8 20:54:05 2018 +0100

    Adjust maximum tested Nextcloud version.

commit 873c4d7
Author: Arno Welzel <github@arnowelzel.de>
Date:   Sun Jul 8 13:58:29 2018 +0200

    Change compatibility information to support Nextcloud 13 as well.

commit 7a7ec5c
Author: Arno Welzel <github@arnowelzel.de>
Date:   Sun Jul 8 01:41:21 2018 +0200

    Less confusing instructions.

commit b6101aa
Author: Arno Welzel <github@arnowelzel.de>
Date:   Sun Jul 8 01:39:30 2018 +0200

    Added explanation how to add the required mimetype mapping.

README.md

@@ -15,6 +15,27 @@ This integrates the two with each other. Just click on a \*.kdbx file in Your Ne
 
 To update to a new version, simply repeat these steps.
 
+## Mimetype detection
+
+Unfortunately, apps can't declare new mimetypes on the fly. To make
+Keeweb work properly, you need to add a new mimetype in the
+`mimetypemapping.json` file (also see the Nextcloud manual at
+https://docs.nextcloud.com/server/14/admin_manual/configuration_mimetypes/index.html).
+
+To proceed, create the file `/config/mimetypemapping.json` (in the `config/` folder at
+Nextcloud’s root directory; the file should be stored next to the `config.php`
+file) or modify the existing one. Make sure, it contains at least the following
+lines:
+
+    {
+    "kdbx": ["x-application/kdbx"]
+    }
+
+After that, run the following command in the root directory of Nextcloud on the server
+(if needed, replace `www-data` with the actual user which is used by the webserver):
+
+    sudo -u www-data php occ files:scan --all
+
 ## Development setup
 
 ```

keeweb/appinfo/info.xml

@@ -14,7 +14,7 @@
     <repository>https://github.com/jhass/nextcloud-keeweb</repository>
     <screenshot>https://cloud.aeshna.de/u/mrzyx/keeweb.gif</screenshot>
     <dependencies>
-        <nextcloud min-version="11" max-version="12" />
+        <nextcloud min-version="11" max-version="15" />
     </dependencies>
     <repair-steps>
         <install>