Fix type hierarchy for CorrectedImageStack, ImagingRetinotopy; improve docs

src/pynwb/data/nwb.base.yaml

@@ -1,6 +1,6 @@
 datasets:
 - neurodata_type_def: NWBData
-  doc: 'The attributes specified here are included in all interfaces.'
+  doc: An abstract data type for a dataset
   attributes:
   - name: help
     dtype: text
@@ -93,14 +93,16 @@ datasets:
     - 4
 groups:
 - neurodata_type_def: NWBContainer
-  doc: The attributes specified here are included in all interfaces.
+  doc: An abstract data type for a generic container storing collections of data
+    and metadata. Base type for all data and metadata containers.
   attributes:
   - name: help
     dtype: text
     doc: Short description of what this type of NWBContainer contains.
 - neurodata_type_def: NWBDataInterface
   neurodata_type_inc: NWBContainer
-  doc: An abstract data type for differentiating experimental data from metadata
+  doc: An abstract data type for a generic container storing collections of data,
+    as opposed to metadata.
 - neurodata_type_def: TimeSeries
   neurodata_type_inc: NWBDataInterface
   doc: General purpose time series.

src/pynwb/data/nwb.ophys.yaml

@@ -303,7 +303,7 @@ groups:
       motion
   groups:
   - neurodata_type_def: CorrectedImageStack
-    neurodata_type_inc: NWBContainer
+    neurodata_type_inc: NWBDataInterface
     doc: One of possibly many.  Name should be informative.
     attributes:
     - name: help

src/pynwb/data/nwb.retinotopy.yaml

@@ -1,6 +1,6 @@
 groups:
 - neurodata_type_def: ImagingRetinotopy
-  neurodata_type_inc: NWBContainer
+  neurodata_type_inc: NWBDataInterface
   doc: 'Intrinsic signal optical imaging or widefield imaging for measuring retinotopy.
     Stores orthogonal maps (e.g., altitude/azimuth; radius/theta) of responses to
     specific stimuli and a combined polarity map from which to identify visual areas.<br

src/pynwb/ecephys.py

@@ -156,8 +156,8 @@ class EventDetection(NWBDataInterface):
                      'source_idx',
                      'times')
 
-    _help_statement = ("Description of how events were detected, such as voltage "
-                       "threshold, or dV/dT threshold, as well as relevant values.")
+    __help = ("Description of how events were detected, such as voltage "
+              "threshold, or dV/dT threshold, as well as relevant values.")
 
     @docval({'name': 'detection_method', 'type': str,
              'doc': 'Description of how events were detected, such as voltage threshold, or dV/dT threshold, \