add compressibility functions X and Y

[Even Solbraa]

Is your feature request related to a problem? Please describe.
add compressibility functions
X = T/v * (∂v/∂T)P og Y = p/v * (∂v/∂p)T

Describe the solution you'd like
implement compressibility function for a phase.

getCompressibilityX()

getCompressibilityY()

[Even Solbraa]

Also add:
isothermal compressibility
κT≡−1/V(∂V∂p)

and
isobaric thermal expansivity

α≡1/V(∂V∂T)p

https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Physical_Chemistry_(Fleming)/04%3A_Putting_the_First_Law_to_Work/4.03%3A_Compressibility_and_Expansivity