Expose JitifyCache via Python interface.

[Robadob]

Required by FLAMEGPU/ABM_Framework_Comparisons#9

To allow

if "--disable-rtc-cache" in sys.argv:
    rtc_cache = pyflamegpu.JitifyCache.getInstance()
    rtc_cache.useMemoryCache(False)
    rtc_cache.useDiskCache(False)

The changes to JitifyCache.h/.cu are required to suppress a SWIG warning, "Nothing known about jitify::experimental::KernelInstantiation".

This will cause conflicts with #1150

[ptheywood]

Added a couple of test cases to programatically check this is exposed, which it is.

I'll let you (@Robadob) merge this once CI passes, assuming you are happy with my tests.