[data_structures]: Priority Queue added

16_priority_q added
[data_structures]: Priority Queue implemented using a 2d array

17_prior_q_2arr added
Each priority level has a row (in the 2d array) which serves as a
circular queue.
[data_structures]: Binary tree implemented using linked array

07_trees folder added
01_bintree_linkarr added
[data_structures]: Binary tree implemented using a sequential array

02_bintree_arr added