Add Support for ncWMS

[brendancol]

This would be an additional service type, or optional extension to the WMS Service to include additional optional parameters specified by ncWMS documentation:

https://reading-escience-centre.gitbooks.io/ncwms-user-guide/content/04-usage.html#wms

@rsignell-usgs I know we are interested in the color range parameters, but this issue here can serve to help specify exactly whats needed some migration to mapshader is straightforward

[brendancol]

• Add additional optional parameters:

COLORSCALERANGE: Of the form min,max this is the scale range used for plotting the data.
NUMCOLORBANDS: The number of discrete colours to plot the data. Must be between 2 and 250
ABOVEMAXCOLOR: The colour to plot values which are above the maximum end of the scale range. Colours are as defined above, with the addition of "extend", which will use the maximum value of the palette.
BELOWMINCOLOR: The colour to plot values which are below the minimum end of the scale range. Colours are as defined above, with the addition of "extend", which will use the minimum value of the palette.
LOGSCALE: "true" or "false" - whether to plot data with a logarithmic scale
TARGETTIME: For in-situ data, all points which fall within the time range (specified in the TIME parameter) will be plotted. In the case that an in-situ point has multiple time readings within that range, the colour used to plot them will depend on the time value which is closest to this given value
TARGETELEVATION: For in-situ data, all points which fall within the elevation range (specified in the ELEVATION parameter) will be plotted. In the case that an in-situ point has multiple elevation readings within that range, the colour used to plot them will depend on the elevation value which is closest to this given value
OPACITY: The percentage opacity of the final output image
ANIMATION: "true" or "false" - whether to generate an animation. This also needs the TIME to be of the formstarttime/endtime, and currently is only implemented for features with a discrete time axis.

[brendancol]

• Add all GetMap Parameters

FORMAT: The supported formats are:
image/png
image/png;mode=32bit
image/gif
image/jpeg
application/vnd.google-earth.kmz
TIME: For gridded data with a discrete time axis this takes a single value. For in-situ data which is spread over a range, it is more useful to provide a time range in the form starttime/endtime. This should ideally be used in conjunction with the TARGETTIME parameter (see below)
ELEVATION: For gridded data with a discrete vertical axis this takes a single value. For in-situ data which is spread over a range, it is more useful to provide an elevation range in the form startelevation/endelevation. This should ideally be used in conjunction with the TARGETELEVATION parameter (see below)
STYLES: Available styles can be found from the Capabilities document. Generally styles are of the form stylename/palettename, and the style name default is always available. The available palettes can be seen in the following image, and additional palettes can be added by following the instructions here: