Catch up schema with changes for adding trial support. See https://gi…

[oruebel]

Motivation

Catch schema up with changes for adding trial structure. See NeurodataWithoutBorders/pynwb#536

Major changes:

• Add DynamicTable neurodata_type for column-based data tables that can be more easily expanded (by adding colmns) without having to create custom extensions
• Add TableColmn neurodata_type to define the column of a DynamicTable data
• Change dtype from generic number to more specific type:
  * to float forSpatialSeries.data
  * to int8 for ImageSeries.data
• Change dtype from unspecified None to more specific type:
  * float for AnnotationSeries.data.conversion, AnnotationSeries.data.resolution, IntervalSeries.data.conversion, IntervalSeries.data.resolution attributes
  * test for AbstractFeatureSerie.data.unit,AnnotationSeries.data.unit, IntervalSeries.data.unit attributes
• Add metadata group of type DynamicTable to Epochs type
• Change Sex to Gender in Subject metadata
• Add trials group for storing trial data

Note

Credit for implementing these changes goes to @ajtritt . I'm just helping with catching up the schema repo.

[oruebel]

Fix #152