add new clang format spec

.clang-format-6

+# This file is part of the dune-gdt project:
+#   https://github.com/dune-community/dune-gdt
+# Copyright 2010-2016 dune-gdt developers and contributors. All rights reserved.
+# License: BSD 2-Clause License (http://opensource.org/licenses/BSD-2-Clause)
+# Authors:
+#   Felix Schindler (2010, 2013, 2016)
+#
+# https://releases.llvm.org/6.0.0/tools/clang/docs/ClangFormatStyleOptions.html
+AlignAfterOpenBracket: true
+AlignConsecutiveAssignments: false
+AlignEscapedNewlines: Right
+AlignOperands: true
+AlignTrailingComments: false
+AllowAllParametersOfDeclarationOnNextLine: true
+AllowShortBlocksOnASingleLine: false
+AllowShortCaseLabelsOnASingleLine: false
+AllowShortFunctionsOnASingleLine: Empty
+AllowShortIfStatementsOnASingleLine: false
+AllowShortLoopsOnASingleLine: false
+AlwaysBreakAfterDefinitionReturnType: None
+AlwaysBreakAfterReturnType: None
+AlwaysBreakBeforeMultilineStrings: false
+AlwaysBreakTemplateDeclarations: true
+BasedOnStyle: Mozilla
+BinPackArguments: false
+BinPackParameters: false
+BreakBeforeBinaryOperators: NonAssignment
+BraceWrapping:
+  SplitEmptyFunction: false
+  SplitEmptyRecord: false
+BreakBeforeTernaryOperators: true
+BreakConstructorInitializers: BeforeComma
+ColumnLimit: 120
+ConstructorInitializerAllOnOneLineOrOnePerLine: false
+ConstructorInitializerIndentWidth: 2
+ContinuationIndentWidth: 4
+Cpp11BracedListStyle: true
+DerivePointerAlignment: false
+ExperimentalAutoDetectBinPacking: false
+FixNamespaceComments: true
+IndentCaseLabels: true
+IndentPPDirectives: AfterHash
+IndentWidth: 2
+IndentWrappedFunctionNames: false
+KeepEmptyLinesAtTheStartOfBlocks: true
+Language: Cpp
+MaxEmptyLinesToKeep: 2
+NamespaceIndentation: None
+PenaltyBreakComment: 60
+PenaltyBreakFirstLessLess: 120
+PenaltyBreakString: 1000
+PenaltyExcessCharacter: 1000000
+PenaltyReturnTypeOnItsOwnLine: 60
+PointerAlignment: Left
+SortIncludes: false
+SpaceAfterCStyleCast: false
+SpaceAfterTemplateKeyword: true
+SpaceBeforeAssignmentOperators: true
+SpaceBeforeParens: ControlStatements
+SpaceInEmptyParentheses: false
+SpacesBeforeTrailingComments: 1
+SpacesInAngles: false
+SpacesInCStyleCastParentheses: false
+SpacesInParentheses: false
+SpacesInSquareBrackets: false
+Standard: Cpp11
+TabWidth: 2
+UseTab: Never