Removed unnecessarily memory allocations
Minor changes
Renamed "phonon_thermodynamics.cpp" and "phonon_thermodynamics.h" as "thermodynamics.cpp" and "thermodynamics.h", respectively.
Renamed Phonon_thermodynamics class as Thermodynamics.
Pointer names are also renamed accordingly.
Removed unnecessary definitions of pointers for interpolation class.
Modified makefiles
A naive tuning of V3. Tuned version is implemented as V3_tune.
The basis idea of this tuning is to reduce the call of std::exp(complex z), which was the most time comsuming part of the computation.
Currently, the tuned version is assumed to work with nkx=nky=nkz.
Merge branch 'feature/tuning0.9.2' into develop