Fixed bug with TTSE with P,H as inputs

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
New interpolation method for TTSE in the last cell before critical point based on y = a*x^(1/n)

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Added scripts to dev to check speed and accuracy of TTSE and BICUBIC interpolation methods.  BICUBIC seems to be on average 5% slower than TTSE

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>