1) Fixed so that all moves that alter edge lengths use the same value
for the minimal edge length, specified via Utils.MIN_EDGE_LENGTH.

2) With a certain probability, LOCALTopologyMove now uses the slower
swapWithUncleAlignToParent move for the topology swaps (by default this
probability is set to 0.1).

3) Implemented simulated annealing scheme, currently switched on/off
via a global variable at the top of Mcmc.java, with a logarithmic
cooling schedule over the first half of the burnin (switched off by
default).