Rename variables

[ahill187]

Description

In this PR, I have renamed the following variables to be in keeping with Python naming conventions and to be more descriptive:

original	new
data, X_data, X_input	x_data
true_labels, true_label, y	y_data_true
labels, PARC_labels	y_data_pred
PARC_labels_array	y_data_pred_array
num_threads	n_threads
N, n_cells, n_elements	n_samples
small_pop	small_community_size
time_small_pop	small_community_timeout
time_smallpop_start	time_start
small_pop_exist	small_community_exists
too_big_factor	large_community_factor
distance	distance_metric
dist_std_local	l2_std_factor
jac_std_global, jac_std_toobig	jac_std_factor
G	graph
G_sim	graph_pruned
sim_list	similarities
sim_list_new	similarities_new
sim_list_array	similarities_array
strong_locs	indices_similar
PARC_labels_leiden	node_communities
set_PARC_labels_leiden	set_node_communities
PARC_labels_leiden_big	node_communities_big
sources	input_nodes
targets	output_nodes
edgelist	edges
edgelist_copy	edges_copy
new_edgelist	new_edges
onevsall_val, onevsall	target
n_cancer	n_target
pbmc_labels	negative_labels
thp1_labels	positive_labels
cluster_i_loc, cluster_ii_loc	community_indices
pop_i, pop_ii	community_size
cluster_ii, cluster_i	community_id
cluster_big_loc	large_community_indices
cluster_big	large_community_id
big_pop	large_community_size

See ShobiStassen#32.