fix(migrations): Fix rebase issues

* Install / Uninstall plugins
* List plugins

.gitignore

@@ -67,7 +67,8 @@ instance/
 
 # Sphinx documentation
 docs/_build/
-docs/
+# pdoc
+docs/html
 
 # PyBuilder
 target/

docs/plugin_development.md

@@ -0,0 +1,57 @@
+# Plugin Development
+
+## File Structure
+
+    - your_plugin/
+        - __init__.py
+        - ...
+        - migrations/ (optional)
+            - ...
+    - setup.cfg
+
+The basic layout of a plugin is quite simple, you will only need the `setup.cfg` or `setup.py` and
+the package containing your plugin code, at lease a `__init__.py` file with your `Plugin` class.
+
+If you use custom database tables you need to provide a `migrations` directory within your package,
+see next section.
+
+## Database Tables / Migrations
+To allow upgrades of installed plugins, the database is versioned and handled
+through [Alembic](https://alembic.sqlalchemy.org/en/latest/index.html) migrations.
+Each plugin, which uses custom database tables, is represented as an other base.
+So you could simply follow the Alembic tutorial on [how to work with multiple bases](https://alembic.sqlalchemy.org/en/latest/branches.html#creating-a-labeled-base-revision).
+
+A quick overview on how to work with migrations for your plugin:
+
+    $ flaschengeist db revision -m "Create my super plugin" \
+      --head=base --branch-label=myplugin_name --version-path=your/plugin/migrations
+
+This would add a new base named `myplugin_name`, which should be the same as the pypi name of you plugin.
+If your tables depend on an other plugin or a specific base version you could of cause add
+
+    --depends-on=VERSION
+
+or
+
+    --depends-on=other_plugin
+
+
+### Plugin Removal and Database Tables
+As generic downgrades are most often hard to write, your plugin is not required to provide such functionallity.
+For Flaschengeist only instable versions provide meaningful downgrade migrations down to the latest stable version.
+
+So this means if you do not provide downgrades you must at lease provide a series of migrations toward removal of
+the database tables in case the users wants to delete the plugin.
+
+    (base) ----> 1.0 <----> 1.1 <----> 1.2
+                  |         
+                  --> removal
+
+After the removal step the database is stamped to to "remove" your
+
+## Useful Hooks
+There are some predefined hooks, which might get handy for you.
+
+For more information, please refer to
+- `flaschengeist.utils.hook.HookBefore` and
+- `flaschengeist.utils.hook.HookAfter`

flaschengeist/cli/docs_cmd.py

@@ -8,7 +8,7 @@ import subprocess
     "--output",
     "-o",
     help="Documentation output path",
-    default="./docs",
+    default="./docs/html",
     type=click.Path(file_okay=False, path_type=pathlib.Path),
 )
 @click.pass_context

flaschengeist/plugins/__init__.py

@@ -1,27 +1,7 @@
 """Flaschengeist Plugins
 
-## Custom database tables
+.. include:: docs/plugin_development.md
 
-You can add tables by declaring them using the SQLAlchemy syntax,
-then use Alembic to generate migrations for your tables.
-This allows Flaschengeist to proper up- or downgrade the
-database tables if an user updates your plugin.
-
-migrations have to be provided in a directory called `migrations`
-next to your plugin. E.G.
-
-    myplugin
-        - __init__.py
-        - other/
-            - ...
-        - migrations/
-
-## Useful Hooks
-There are some predefined hooks, which might get handy for you.
-
-For more information, please refer to
-- `flaschengeist.utils.hook.HookBefore` and
-- `flaschengeist.utils.hook.HookAfter`
 """
 
 from typing import Optional