[BuildSystem] Made header list more patch friendly.

To make future patches more readable the list of headers is now ordered
alphabetically with one header per line.

dune/istl/paamg/CMakeLists.txt

 add_subdirectory("test" EXCLUDE_FROM_ALL)
 
 #install headers
-install(FILES aggregates.hh dependency.hh galerkin.hh graph.hh
-          indicescoarsener.hh properties.hh globalaggregates.hh
-          hierarchy.hh construction.hh
-          transfer.hh smoother.hh amg.hh kamg.hh combinedfunctor.hh
-          graphcreator.hh parameters.hh renumberer.hh pinfo.hh
-	DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/dune/istl/paamg)
+install(FILES
+  aggregates.hh
+  amg.hh
+  combinedfunctor.hh
+  construction.hh
+  dependency.hh
+  galerkin.hh
+  globalaggregates.hh
+  graph.hh
+  graphcreator.hh
+  hierarchy.hh
+  indicescoarsener.hh
+  kamg.hh
+  parameters.hh
+  pinfo.hh
+  properties.hh
+  renumberer.hh
+  smoother.hh
+  transfer.hh
+  DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/dune/istl/paamg)

dune/istl/paamg/Makefile.am

 SUBDIRS = test
 
 paamgdir = $(includedir)/dune/istl/paamg
-paamg_HEADERS = aggregates.hh dependency.hh galerkin.hh graph.hh \
-	indicescoarsener.hh properties.hh globalaggregates.hh \
-	hierarchy.hh construction.hh \
-	transfer.hh smoother.hh amg.hh kamg.hh combinedfunctor.hh \
-	graphcreator.hh parameters.hh renumberer.hh pinfo.hh \
-	fastamg.hh fastamgsmoother.hh
+paamg_HEADERS = aggregates.hh          \
+	amg.hh                         \
+	combinedfunctor.hh             \
+	construction.hh                \
+	dependency.hh                  \
+	fastamg.hh                     \
+	fastamgsmoother.hh             \
+	galerkin.hh                    \
+	globalaggregates.hh            \
+	graph.hh                       \
+	graphcreator.hh                \
+	hierarchy.hh                   \
+	indicescoarsener.hh            \
+	kamg.hh                        \
+	parameters.hh                  \
+	pinfo.hh                       \
+	properties.hh                  \
+	renumberer.hh                  \
+	smoother.hh                    \
+	transfer.hh
 
 include $(top_srcdir)/am/global-rules