Add array objects with finalizer to pass GC test

Add calls to fftw_free
Disable R2C functions until real arrays are defined
Add copying and in-place FFT functions

Rename ArrayXd to ArrayXD, etc.
Rename Alloc to NewArray
Hide Plan
Remove plans from tests
Moved into fftw directory
Simplify public functions

Re-expose Plan.
Remove .FFT() to reduce clutter.
Simplify FFT() and make IFFT() distinct.
Rename Array2D to Array2, FFT2D to FFT2.
Fix doc typo
Add missing package name in doc
Replace nested slices with contiguous
Update doc for NewArray
Fix bug in IFFT2

Add At() and Set() to 1D Array
Remove use of fftw_malloc and finalizers

Finalizers were used to free malloc'd memory and to destroy plans
Update doc to reflect changes
Added a 32-bit package