webpivottalbes uses this to display cell value in pivot table

because webpivottable only understand this

not sure why, but these changes look working for pivot table without
any dimensions on webpivottable

webpivottable uses xsd: prefix to convert types. Without this, measure
dimension is not detected as measure.

Based on https://github.com/abilian/olapy/tree/simple_example_wendelin ,
but using directly numpy arrays for simplicity.

support OPTIONS request, that is needed for https

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