Hides download button and adds message when download estimator calculates Zero bytes
Remove common function _downloadUrl and use inheritance to override behaviour.
Removing unnecessary constructors
Remove unused function
Download handlers can now be asked if the know how to estimate the size of a download.
Add download estimation behaviours to BodaacDownloadHandler
Rename download estimate function
Update DownloadEstimator to use new functionality in DownloadHandlers
Remove the downloadUrl() functionality from Injectors as it is no longer used
Remove more unused code
Trying to find a better function name
Whoops. No argument needed here.
Rearranging methods to be close to first usgae
Refactor behaviour out of DownloadEstimator and into BaseInjector.

Move some behaviour up from subclasses into BaseInjector.

Tidied tests for WmsInjector and NcwmsInjector.
Merge pull request #1283 from aodn/download_estimator_uses_metadata

Download estimator uses metadata