Documentation updates, enhancements and bug fixes

New features

• maximal stimulus display framerate can be set
• added a new conditional stimulus that has a different conditions for the two possible switches
  (stim_on->stim_off) on condition_off and and (stim_on->stim_off) on condition_on
  This enables the TwoRadiusCenteringWrapper, a centering stimulus which appears when the fish disappears
  from the outer border and disappears when the fish is close to the center.
• more improvements to conditional stimuli, please see API documentation for stimuli/conditional.
• fish position estimator also allows querying velocity

Fixes

• after long runs, Stytra does not hang on exit anymore (fix in ArrayQueues 1.2)
• remaining protocol duration estimate is refreshed during execution, so protocols
  whose duration depends on the animal behavior (such as those with a CenteringWrapper)
  display more sensible numbers.
• Stytra version, in addition to condition, is now saved
• single source for log names, so that metadata corresponds to file names
• the accumulators keep only a partial history if the protocol is not running, in order to
  prevent overflowing the memory.
• fixed crash on capturing camera image if the experiment was not started yet

Changes in default behavior

• CenteringWrapper has the radial centering stimulus by default, the non-centering
  stimulus is specified as the stimulus keyword argument

Documentation updates

• large reorganization and inclusion of the mansucript