Rename upper-layer preference:  "enableBreakpointDetection" --> "splitting".

This was done with

  sed -i -e 's/enableBreakpointDetection/splitting/' \
      $(grep -rl enableBreakpointDetection *)

and a little manual tweaking to the documentation and the tests.
Rename upper-layer preference:  "enableSingularityDetection" --> "blowup".

This was done with

  sed -i -e 's/enableSingularityDetection/splitting/' \
      $(grep -rl enableSingularityDetection *)

and a little manual tweaking to fix documentation and tests.

NB:  This rename does NOT mean that this preference behaves semantically like
the v4 "blowup" preference.  This _only_ controls whether or not singularity
detection is enabled, not what singularities are searched for.  The changes
required to update these semantics will be done separately.
Map singPrefs --> blowupPrefs.
Map breakpointPrefs --> splitPrefs.
Merge branch 'fix-rename-prefs' into development

Conflicts:
	@chebfun/constructor.m