Working implementation of settable experiment_spot_design and experiment_library_design.

Supporting work includes web resources for experiment_library_design, experiment_spot_design_read_spec, and experiment_spot_design (for error checking). This includes tests for those web resources and tests for modifications to the MetadataPlugin in order to access the two new fields. Modifications to Jaxb (lists of convertable classes), context, and existing experiment web resources were also made.