deprecate start/stop/step in AnalysisBase.__init__()

[orbeckst]

In preparation for #1463 where we want analysis classes to use start, stop, step in the run() method only, we need to deprecate the use in

• analysis.base.AnalysisBase.__init__:

  mdanalysis/package/MDAnalysis/analysis/base.py

  Line 92 in 1a1b2f1

  def __init__(self, trajectory, start=None,

• custom analysis classes (git grep 'start=.*stop=')
  • density.py
  • diffusionmap.py (clean-up only, already uses AnalysisBase)
  • hbonds/hbond_analysis.py
  • hbonds/wbridge_analysis.py
  • rms.py (removed the deprecation for start/stop/step in run()!)