Change use of t_inpfile to std::vector
Refactored code to use std::vector for t_inpfile instead of pointers.
This is meant to be the basis for a change in mdp file writing from gmx
dump that requires the t_inpfile structure to use the already available
functions to write the file instead of having a custom one.
Rebased on change that changes the use of macros to functions for
reading the information into the structure.
Changed t_inpfile to a struct with constructor and destructor, as well as
replacing the custom sort function with std::sort.
Change-Id: I0c5c646b183d232c638db869f98457af82e0be18