Added API documentation, still much room for improvement.

api.md

@@ -5,4 +5,31 @@ permalink: "/api"
 order: 200
 categories: api
 ---
-I'm not quite sure yet what to put here. For now, see [Jabit's JavaDoc](http://www.javadoc.io/doc/ch.dissem.jabit/jabit-core/1.0.1)
+> See [Jabit's JavaDoc](http://www.javadoc.io/doc/ch.dissem.jabit/jabit-core/1.0.1) for a detailed documentation of all classes and methods. Feel free to either open an issue or create a pull request if you find something to be unclear or incorrect.
+{: .info}
+
+# Context Setup
+The `BitmessageContext` provides all methods a usual Bitmessage client needs. Note that all its methods should be thread safe, but you'll need to check your `BitmessageContext.Listener` for thread safety. The listener may even be called simultaneously from different threads.
+
+To keep the library small, flexible and independent from (but compatible to) heavy-duty frameworks such as Spring, the `BitmessageContext` needs to be initialized with all its dependencies.
+
+# Creating Identities
+
+{% highlight java %}
+BitmessageAddress identity = ctx.createIdentity(false, Pubkey.Feature.DOES_ACK);
+{% endhighlight %}
+
+If _shorter_ is enabled, Jabit searches a private key that yields a slightly shorter address. This is not optimized and may take a long time to complete.
+
+# Importing Identities
+Identities can be imported from PyBitmessages keys.dat by using the WifImporter from the library `jabit-wif`. The constructor needs a `BitmessageContext` and either a file, a string representation of a keys.dat or an input stream. The importer will throw an exception if the data can't be parsed.
+
+Once constructed you can choose to list the contained identities, import all, a subset or a specific identity into the given `BitmessageContext`.
+
+# Exporting Identities
+Exports work very similar to imports. A `WifExporter` also needs a `BitmessageContext` to construct. You then can add either all or specific identities to the importer. Id you provide specific identities, make sure they have a private key. They will not be reloaded.
+
+If you're done adding identities, call one of the `write` methods to save the exported identities, or `toString()` for the string representation.
+
+# Threads
+> TODO