Enhance aur_get()

[asiripanich]

• Make GetFeature's params as arguments of aur_get().

See https://docs.geoserver.org/latest/en/user/services/wfs/reference.html.

# instead of this
aur_get(.x, params = list(maxFeatures = 10))
# user will be able to do this along with other parameters.
aur_get(.x, maxFeatures = 10)

• Handle count and maxFeatures correctly according to the version argument.
• Allow different outputFormats to be read into R. See https://docs.geoserver.org/latest/en/user/services/wfs/outputformats.html for available formats of GetFeature.
• Rename the existing arguments to match with the GetFeature parameters, except for typename.

[asiripanich]

Note that, 'maxFeatures' is deprecated in WFS GetFeature 2.0.0 and replaced by 'count'.