Add basic interpolator and decimator to change sample rates by a factor
of a prime number. Interpolator repeats samples forming a stair signal,
while decimator drops excessive samples.
Templates have been used to utilize fast integer operations contrary to
byte-by-byte operations for number of bit width vs channel count
combinations.
Signed-off-by: Marcin Smoczyński <smoczynski.marcin@gmail.com>
