OCL device code - replaced float3* by float*

The host code allocates device buffers of type float3 for (number of
elements * sizeof(float) * 3) bytes, but sizeof(float3) is 4x4 = 16
bytes.
As a consequence, float3* buffers have been replaced by float* buffers
and the access to x, y, z components is done by correctly computing the
index.
x -> new_index = 3 * old_index + 0
y -> new_index = 3 * old_index + 1
z -> new_index = 3 * old_index + 2
Replaced one more sizeof(cl_float3) by sizeof(rvec)
Removed comment
Removed command_queue from ocl_gpu_info_t
Added calls to nbnxn_ocl_free, nbnxn_ocl_wait_gpu

TO DO: add implementation for these functions. They are currently empty.
Merge pull request #1 from StreamComputing/asc

Asc