tests: Cleanup imports
metainfo: Don't catch ValueErrors when parsing json.
client: Added classmethod for querying datasets info
mockserver: Updated docstring for planned changes to h5 file structure.
mockserver: Refactored method of selecting handlers for each supported REST command.
(Adding support for new commands is much cleaner now.)
server: Adapt to new hdf5 structure
server: implemented query for datasets info (needs more testing)
mockserver: Added start() classmethod.
Added simple ContentsBrowser gui.