simplify Matrix class and add elementwise lookup table

[5000user5000]

In PR #18, I simplified the matrix class with only basic functions,such as constructor,getter/setter.
In addition,I put other required functions into several .hpp. For instance,layout,storage_policies(define int4 or other data type) and matrix operations rather than putting all thing in a large class.
For lut,I used element-wise way to save all results of multiplication product to do mixed-precision multiplication (e.g. int4 x int16).