IPPL-2.4.0

Major changes

• Use Kokkos::complex directly in Heffte (#115)
• Added curl operator (#124)
• Added clang format (!155, !159, !160)
• Removed hard-coded types (#142)
• Added Hessian operator (#135)
• Added Bi-harmonic solver (#137)

Minor changes

• Various bug fixes and minor changes (#117, #120, #130, #132, #140, #141, #143, #144, #145, #147, !125)