Allow for modification of featurization settings without a recompile

[Yutong Zhao]

We'd want to be able to dynamically adjust:

const int MAX_ATOM_TYPES = 4;

const int NUM_R_Rs = 16;
const int RADIAL_FEATURE_SIZE = MAX_ATOM_TYPES * NUM_R_Rs;

const float R_eta = 16;
const float R_Rc = 4.6;

const float A_Rc = 3.1;
const float A_eta = 6.0;
const float A_zeta = 8.0;
const int NUM_A_THETAS = 8;
const int NUM_A_RS = 4;

const int ANGULAR_FEATURE_SIZE = NUM_A_RS * NUM_A_THETAS * (MAX_ATOM_TYPES * (MAX_ATOM_TYPES+1) / 2);

const int TOTAL_FEATURE_SIZE = RADIAL_FEATURE_SIZE + ANGULAR_FEATURE_SIZE;

__device__ const float R_Rs[NUM_R_Rs] = {...};

__device__ const float A_thetas[NUM_A_THETAS] = {...}
};

__device__ const float A_Rs[NUM_A_RS] = {...};

And be able to support multiple atom types without a recompile

[Yutong Zhao]

Partially implemented. Still need a recompile for performance reasons.