doc/faq: fix emphasis in bold text

ReST does not support nested markup, i.e., no bold italic.
doc: update all benchmarks for 1.0-alpha1

The benchmarks were run at the MPI-IS Stuttgart, except for the K20Xm
test. The latter used ½ node of the supercomputer Hydra at the RZG.

For comparison: running the Lennard-Jones benchmark for 62,500 particles
with LAMMPS (27 Aug 2013) on Hydra yields:

== Intel Sandy Bridge nodes ==
 16 cores (1 node):  63 ns/step/particle
 32 cores (2 nodes): 36 ns/step/particle
 64 cores (4 nodes): 21 ns/step/particle

== Intel Ivy Bridge nodes ==
 20 cores (1 node):  45 ns/step/particle
 50 cores (3 nodes): 22 ns/step/particle
 60 cores (3 nodes): 18 ns/step/particle
 80 cores (4 nodes): 14 ns/step/particle
160 cores (8 nodes):  9 ns/step/particle
doc/usage: update page numbers for paper on H5MD