Fixed bug

uninitialized variable (from last commit)
adaptive: regtest, sigma in timesteps, corrected flaw

Now, for consistency, the time units of SIGMA in METAD for the
ADAPTIVE=DIFF scheme is in timesteps to be consistent with the rest of
the program. Documentation, printout and regtests are done.
Changed stride in pathmsd: now in timesteps

Now the stride for the neighbor lists in the path implementation
are in timesteps. By now this means that PATHMSD and PROPERTYMAP are
defined with e.g. NEIGH_STRIDE=5
Consistent weights for weighted and nonweighted RMSD TYPE=OPTIMAL
sum_hills has a default --bin set to 50