doc: Update more docstrings to have one sentence summary as first line. Reviewed io, java, linear-algebra, prefs, and set script directories. * scripts/io/beep.m, scripts/io/dlmwrite.m, scripts/io/importdata.m, scripts/io/strread.m, scripts/io/textread.m, scripts/java/javaArray.m, scripts/java/java_get.m, scripts/java/java_set.m, scripts/java/javaaddpath.m, scripts/java/javachk.m, scripts/java/javaclasspath.m, scripts/java/javamem.m, scripts/java/javarmpath.m, scripts/linear-algebra/bandwidth.m, scripts/linear-algebra/commutation_matrix.m, scripts/linear-algebra/cond.m, scripts/linear-algebra/condest.m, scripts/linear-algebra/cross.m, scripts/linear-algebra/duplication_matrix.m, scripts/linear-algebra/expm.m, scripts/linear-algebra/housh.m, scripts/linear-algebra/isdefinite.m, scripts/linear-algebra/ishermitian.m, scripts/linear-algebra/issymmetric.m, scripts/linear-algebra/istril.m, scripts/linear-algebra/istriu.m, scripts/linear-algebra/krylov.m, scripts/linear-algebra/logm.m, scripts/linear-algebra/normest.m, scripts/linear-algebra/null.m, scripts/linear-algebra/onenormest.m, scripts/linear-algebra/orth.m, scripts/linear-algebra/qzhess.m, scripts/linear-algebra/rank.m, scripts/linear-algebra/rref.m, scripts/linear-algebra/vech.m, scripts/path/matlabroot.m, scripts/prefs/addpref.m, scripts/prefs/getpref.m, scripts/prefs/ispref.m, scripts/prefs/rmpref.m, scripts/prefs/setpref.m, scripts/set/powerset.m, scripts/set/setdiff.m: Update more docstrings to have one sentence summary as first line.

--- a/scripts/prefs/ispref.m
+++ b/scripts/prefs/ispref.m
@@ -17,17 +17,18 @@
 ## <http://www.gnu.org/licenses/>.
 
 ## -*- texinfo -*-
-## @deftypefn {Function File} {} ispref (@var{group}, @var{pref})
-## Return true if the named preference @var{pref} exists in the
-## preference group @var{group}.
+## @deftypefn  {Function File} {} ispref (@var{group}, @var{pref})
+## @deftypefnx {Function File} {} ispref (@var{group})
+## Return true if the named preference @var{pref} exists in the preference
+## group @var{group}.
 ##
 ## The named preference group must be a character string.
 ##
-## The preference @var{pref} may be a character string or a cell array
-## of character strings.
+## The preference @var{pref} may be a character string or a cell array of
+## character strings.
 ##
-## If @var{pref} is not specified, return true if the preference
-## group @var{group} exists.
+## If @var{pref} is not specified, return true if the preference group
+## @var{group} exists.
 ## @seealso{getpref, addpref, setpref, rmpref}
 ## @end deftypefn