Fix docs missing DetectorPlatformClient class

In #131, we turned APIClient into an alias for DetectorPlatformClient,
but that broke the docs since calling :members: on APIClient wouldn't
display any functions

So this adds both APIClient and DetectorPlatformClient to the API docs

Author: julienr

docs/api.rst

@@ -3,36 +3,31 @@ API
 ===
 
 
-DetectorPlatformClient
-----------------------
+Detector Platform
+-----------------
 
-.. autoclass:: picterra.APIClient
+.. autoclass:: picterra.DetectorPlatformClient
     :members:
 
+.. autoclass:: picterra.APIClient
+    :members:
 
-PlotsAnalysisPlatformClient
----------------------------
-
-.. autoclass:: picterra.PlotsAnalysisPlatformClient
+.. automodule:: picterra.nongeo
     :members:
 
 
-Pagination
-----------
+Plots Analysis Platform
+-----------------------
 
-.. autoclass:: picterra.ResultsPage
+.. autoclass:: picterra.PlotsAnalysisPlatformClient
     :members:
 
 
-nongeo
-------
+Utility classes
+---------------
 
-.. automodule:: picterra.nongeo
+.. autoclass:: picterra.ResultsPage
     :members:
 
-
-Exceptions
-----------
-
 .. autoclass:: picterra.APIError
     :members: