Fix sideset keyboard short cuts

\sideset1 can't be entered via keyboard, so I renamed the commands.

lib/Makefile.am

@@ -1110,9 +1110,9 @@ dist_imagesmath_DATA = \
 	images/math/shortrightarrow.png \
 	images/math/shortuparrow.png \
 	images/math/sideset.png \
-	images/math/sideset1.png \
-	images/math/sideset2.png \
-	images/math/sideset3.png \
+	images/math/sidesetl.png \
+	images/math/sidesetn.png \
+	images/math/sidesetr.png \
 	images/math/sigma.png \
 	images/math/sigma2.png \
 	images/math/sim.png \

lib/ui/stdtoolbars.inc

@@ -184,9 +184,9 @@ ToolbarSet
 		Item "Insert integral" "math-insert \int"
 		Item "Insert product" "math-insert \prod"
 		Item "Insert left/right side scripts" "math-insert \sideset"
-		Item "Insert right side scripts" "math-insert \sideset1"
-		Item "Insert left side scripts" "math-insert \sideset2"
-		Item "Insert side scripts" "math-insert \sideset3"
+		Item "Insert right side scripts" "math-insert \sidesetr"
+		Item "Insert left side scripts" "math-insert \sidesetl"
+		Item "Insert side scripts" "math-insert \sidesetn"
 		Separator
 		Item "Insert ( )" "math-delim ( )"
 		Item "Insert [ ]" "math-delim [ ]"

src/mathed/MathFactory.cpp

@@ -539,11 +539,11 @@ MathAtom createInsetMath(docstring const & s, Buffer * buf)
 	if (s == "sideset")
 		return MathAtom(new InsetMathSideset(buf, true, true));
 	// The following 3 string values are only for math toolbar use, no LaTeX names
-	if (s == "sideset1")
+	if (s == "sidesetr")
 		return MathAtom(new InsetMathSideset(buf, false, true));
-	if (s == "sideset2")
+	if (s == "sidesetl")
 		return MathAtom(new InsetMathSideset(buf, true, false));
-	if (s == "sideset3")
+	if (s == "sidesetn")
 		return MathAtom(new InsetMathSideset(buf, false, false));
 	if (isSpecialChar(s))
 		return MathAtom(new InsetMathSpecialChar(s));