This reverts commit 06612300.

change ring communication API to no longer require a static variable pointing to 'this' of the caller

with sparse and hybrid systems, Pair::ev_tally() may not be called on
every processor and thus the computes in USER-TALLY may hang during
reverse communication because of the error->all() call after checking
whether callback from Pair::ev_tally() has been called at least once.
To address this cleanly, a second callback function needs to be added,
which is run during Pair::ev_setup() and will now handle all memory
re-allocation and clearing of accumulators, just like it is done for
regular tallied data.

- make heatj a pointer instead of a static array
- fix memory leaks for eatom, stress
- simplify and streamline computation

correctly skip over point particles and point dipoles when counting extendend particles in fix rigid/small

change incorrect EINERTIA constant in rigid body integrators from 4.0 to 2.0 (same as in other integrators)

add restart support to fix deform. only "initial" data is restored and some consistency check performed

MAINT: Turned 'global' options into a 'thermo yes'/'thermo no' option that enables dumping of thermo data to the netcdf file (for parallel NetCDF/MPIIO variant).

MAINT: Turned 'global' options into a 'thermo yes'/'thermo no' option that enables dumping of thermo data to the netcdf file.

make pair styles lj/cut/tip4p/long/omp, lj/long/tip4p/long and lj/long/tip4p/long/omp consistent with the reset of tip4p styles

MAINT: Switched NetCDF from 64BIT_OFFSET to 64BIT_DATA which can handle frames (of unlimited dimension) > 2 GB. This becomes important for system sizes 100 Mio atoms and upwards.