Add progress hash bar output to affineEnsemble when doing main steps
Add progress hash bar, bump version number to 0.2.8

* Add new hashbar class, which makes a hash progress bar.
  Use it in affineEnsemble::masterSample() when verbosity=1.
  For higher verbosities, other outputs will interfere with
  the progress bar.
* Change initial_position to InitialPosition in HDF5 output.
* Bump version number of base to 0.2.8
Small modifications to hashbar.

* Add initialize method to hashbar for initial (empty) output;
  previous usage meant nothing was output until the first hash
  was drawn.
* Add ability to specify character used in hashbar (def: '#')
* Use new methods in affineEnsemble