Adding R interface functions
Various neighbourhood calculation fixes
Fixing indexing bug
Adding and using typedefs
Handling 1D input with no "dim" attribute
Fixes to main resampler code
Dealing with requests for a even-width neighbourhood
Making Kernel::evaluate virtual (as it should have been)
Generalising sampling scheme
Fixing problem with my understanding of polymorphism in C++
Exposing a function to R for sampling from a kernel
Adding initial R interface