Change method for generating Java from xml schema files, so that only one generated-sources folder
needs to be added to the build path. Unfortunately, it doesn't seem to add the generated-sources folder
to the build path automatically.
update pa channel schema files.
Add full images to channels.
 - refactor image simplification code out into separate image simplifier.
 - rework channel simplification to populate new images field on both channels and channel history
elements.
Add forceUpdate element to jaxb2 executions, to ensure that files are regenerated, as
stale flag seems to be ineffective. also remove duplicate maven-compiler-plugin element.
Improve error messages for 404 and 400 on channel(group)s endpoints
Only create history entries for images / titles with non-null start dates.
Move cassandra properties out to environment properties files, to make cassandra more configurable.
Ensure ImageTheme defaults sensibly on channels ingest.
Update stage cassandra keyspace to be Atlas_Stage