wcst_import should be able to run on a different host than petascope

[Vlad Merticariu]

Running wcst_import on a different machine than petascope is currently not supported, because there is no implemented way to get the data from the machine where wcst_import sits to the machine where petascope sits.

wcst_import currently sends a POST request to petascope, containing the WCST specific parameters which include the coverage file (in GML). Inside the GML, the binary data of the coverage is referenced through a file path.

In order to support wcst_import running on a different host than petascope the following are needed:

• in the WCST POST request that wcst_import sends, the binary data representing the file contents must be sent along. This can be achieved, for example, by making the request multipart (to avoid adding further non standard parameters, but that could be an option as well).
• an option has to be added in the ingredients of wcst_import, so wcst_import knows to send the data along (when it's on the same host as petascope it doesn't make sense to do the extra transfer)
• in the InsertCoverage and UpdateCoverage handlers of petascope, the data from the request has to be forwarded in the rasql queries instead of file paths.