update formatter to use 11 compliance (#927)

contrib/formatter.xml

@@ -48,7 +48,7 @@
 <setting id="org.eclipse.jdt.core.formatter.blank_lines_before_new_chunk" value="1"/>
 <setting id="org.eclipse.jdt.core.formatter.insert_space_before_binary_operator" value="insert"/>
 <setting id="org.eclipse.jdt.core.formatter.blank_lines_before_package" value="0"/>
-<setting id="org.eclipse.jdt.core.compiler.source" value="1.8"/>
+<setting id="org.eclipse.jdt.core.compiler.source" value="11"/>
 <setting id="org.eclipse.jdt.core.formatter.insert_space_after_comma_in_enum_constant_arguments" value="insert"/>
 <setting id="org.eclipse.jdt.core.formatter.insert_space_after_opening_paren_in_constructor_declaration" value="do not insert"/>
 <setting id="org.eclipse.jdt.core.formatter.comment.format_line_comments" value="true"/>
@@ -173,7 +173,7 @@
 <setting id="org.eclipse.jdt.core.formatter.insert_space_after_opening_bracket_in_array_reference" value="do not insert"/>
 <setting id="org.eclipse.jdt.core.formatter.alignment_for_arguments_in_qualified_allocation_expression" value="16"/>
 <setting id="org.eclipse.jdt.core.formatter.insert_space_after_and_in_type_parameter" value="insert"/>
-<setting id="org.eclipse.jdt.core.compiler.compliance" value="1.8"/>
+<setting id="org.eclipse.jdt.core.compiler.compliance" value="11"/>
 <setting id="org.eclipse.jdt.core.formatter.continuation_indentation_for_array_initializer" value="2"/>
 <setting id="org.eclipse.jdt.core.formatter.insert_space_between_empty_brackets_in_array_allocation_expression" value="do not insert"/>
 <setting id="org.eclipse.jdt.core.formatter.insert_space_before_at_in_annotation_type_declaration" value="insert"/>
@@ -251,7 +251,7 @@
 <setting id="org.eclipse.jdt.core.formatter.insert_space_after_comma_in_constructor_declaration_throws" value="insert"/>
 <setting id="org.eclipse.jdt.core.formatter.alignment_for_parameters_in_method_declaration" value="16"/>
 <setting id="org.eclipse.jdt.core.formatter.insert_space_before_closing_brace_in_array_initializer" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.compiler.codegen.targetPlatform" value="1.8"/>
+<setting id="org.eclipse.jdt.core.compiler.codegen.targetPlatform" value="11"/>
 <setting id="org.eclipse.jdt.core.formatter.alignment_for_resources_in_try" value="80"/>
 <setting id="org.eclipse.jdt.core.formatter.use_tabs_only_for_leading_indentations" value="false"/>
 <setting id="org.eclipse.jdt.core.formatter.alignment_for_arguments_in_annotation" value="16"/>