Add ox and some tooling.
Initial spec to check performance of dav4rack propfind.
Use ox for properties and propstats (doesn’t work with multiple namespaces yet)
Add ox as gem dependency.
Ox requires a string or an ox element, so explicitly convert to a string.
Switch multistatus to completely use ox
Make it possible to cache an array of property responses.
Ox elements can’t be serialized/cached, but the strings to initialize raw elements can.
Map is not needed here.
Raise shouldn’t be used in a normal flow, as it’s pretty expensive.

(for 1000 items, we got 120ms just for raising)
Performance improvements:
don’t dup everything, not needed anyway: 100ms/1000 items
don’t initiate the callbacks, not using them anyway: 140ms/1000items
Use each iso for loops.
Merge branch 'ox-perf-test'