OGR importer

[SoerenHoffstedt]

The OGR importer creates Json dataset files and adds all the provided necessary parameter into the layer definition. On one import only one layer can be added. But a dataset can also be appended by other layers. The added layer can use the same files or copy new files. WFS links are also supported by skipping the file copying.

The changes:

• OGRSource: filename can now also be defined in layer and dataset definition. This allows "virtual" OGR datasets, where one dataset in Mapping can reference layers from different files.
• OGRSource: Fixed bug, not ignoring the layers provenance information anymore.
• EnumConverter: added a method to check if an enum has a value and include guard.
• UploaderUtil: Helper functions for checking information about uploads, used in OGRImporter.
• Uploader unittest: Setting the uploader.directory back to its original value after the test is done.
• OGRImporter: All parameters are put into the layer definition.
• OGRImporter: It is tested if the file can be opened and if it has the added layer.
• OGRImporter: Multiple layers can be added to a dataset, one layer per import. So the datasets can be appended. Appending has to be explicitly by setting append_dataset parameter true.
• OGRImporter: Added WFS support. Skipping file copying when WFS link is detected in main_file. Expects upload_name to be empty.