Add .clang-format file for json

Almost with same configuration used this far in the software. Minor
changes here and there might occur.

.clang-format

@@ -0,0 +1,138 @@
+---
+# Clang-format settings for nlohmann/json
+# For more information, see https://clang.llvm.org/docs/ClangFormatStyleOptions.html
+
+# Language and general settings
+Language:        Cpp
+Standard:        Cpp11
+DisableFormat:   false
+
+# Indentation
+AccessModifierOffset: -2
+ConstructorInitializerIndentWidth: 4
+ContinuationIndentWidth: 0
+IndentCaseLabels: true
+IndentPPDirectives: None
+IndentWidth:     4
+IndentWrappedFunctionNames: false
+NamespaceIndentation: None
+ObjCBlockIndentWidth: 2
+TabWidth:        4
+UseTab:          Never
+
+# Alignment
+AlignAfterOpenBracket: Align
+AlignConsecutiveAssignments: false
+AlignConsecutiveDeclarations: false
+AlignEscapedNewlines: Right
+AlignOperands:   true
+DerivePointerAlignment: false
+PointerAlignment: Left
+AlignTrailingComments: true
+
+# Braces
+BreakBeforeBraces: Custom
+Cpp11BracedListStyle: true
+BraceWrapping:
+  AfterClass:      true
+  AfterControlStatement: true
+  AfterEnum:       false
+  AfterFunction:   true
+  AfterNamespace:  true
+  AfterObjCDeclaration: true
+  AfterStruct:     true
+  AfterUnion:      true
+  AfterExternBlock: false
+  BeforeCatch:     false
+  BeforeElse:      true
+  IndentBraces:    false
+  SplitEmptyFunction: false
+  SplitEmptyRecord: true
+  SplitEmptyNamespace: true
+
+# Wrapping
+ColumnLimit:     120
+AlwaysBreakAfterDefinitionReturnType: None
+AlwaysBreakAfterReturnType: None
+AlwaysBreakBeforeMultilineStrings: false
+AlwaysBreakTemplateDeclarations: true
+BreakBeforeBinaryOperators: None
+BreakBeforeInheritanceComma: false
+BreakBeforeTernaryOperators: true
+BreakConstructorInitializersBeforeComma: false
+BreakConstructorInitializers: BeforeColon
+BreakAfterJavaFieldAnnotations: false
+BreakStringLiterals: true
+AllowAllParametersOfDeclarationOnNextLine: true
+AllowShortBlocksOnASingleLine: false
+AllowShortCaseLabelsOnASingleLine: false
+AllowShortFunctionsOnASingleLine: Empty
+AllowShortIfStatementsOnASingleLine: false
+AllowShortLoopsOnASingleLine: false
+BinPackArguments: true
+BinPackParameters: true
+ExperimentalAutoDetectBinPacking: false
+
+# Comments
+ReflowComments:  false
+CommentPragmas:  '^ IWYU pragma:'
+
+# Empty lines
+KeepEmptyLinesAtTheStartOfBlocks: true
+MaxEmptyLinesToKeep: 1
+
+# Spacing
+SpaceAfterCStyleCast: false
+SpaceAfterTemplateKeyword: false
+SpaceBeforeAssignmentOperators: true
+SpaceBeforeParens: ControlStatements
+SpaceInEmptyParentheses: false
+SpacesBeforeTrailingComments: 1
+SpacesInAngles:  false
+SpacesInContainerLiterals: true
+SpacesInCStyleCastParentheses: false
+SpacesInParentheses: false
+SpacesInSquareBrackets: false
+ObjCSpaceAfterProperty: false
+ObjCSpaceBeforeProtocolList: true
+
+# Includes
+SortIncludes:    true
+IncludeBlocks:   Preserve
+IncludeCategories:
+  - Regex:           '^"(llvm|llvm-c|clang|clang-c)/'
+    Priority:        2
+  - Regex:           '^(<|"(gtest|gmock|isl|nlohmann)/)'
+    Priority:        3
+  - Regex:           '.*'
+    Priority:        1
+IncludeIsMainRegex: '(Test)?$'
+SortUsingDeclarations: true
+
+# Namespaces
+FixNamespaceComments: true
+CompactNamespaces: false
+
+# Classes
+ConstructorInitializerAllOnOneLineOrOnePerLine: false
+
+# Macros
+MacroBlockBegin: ''
+MacroBlockEnd:   ''
+
+# Penalties
+PenaltyBreakAssignment: 2
+PenaltyBreakBeforeFirstCallParameter: 19
+PenaltyBreakComment: 300
+PenaltyBreakFirstLessLess: 120
+PenaltyBreakString: 1000
+PenaltyExcessCharacter: 1000000
+PenaltyReturnTypeOnItsOwnLine: 60
+
+# Misc
+RawStringFormats:
+  - Delimiter:       pb
+    Language:        TextProto
+    BasedOnStyle:    google
+...
+