Add clang-format

- format is based on LLVM format with a bunch of customizations
- clang-format is deactivated in the `packages` directory

.clang-format

+---
+BasedOnStyle: LLVM
+AccessModifierOffset: '-1'
+AlignConsecutiveAssignments: 'false'
+AlignEscapedNewlines: Left
+AlignOperands: 'true'
+AlignTrailingComments: 'true'
+AllowAllParametersOfDeclarationOnNextLine: 'false'
+AllowShortIfStatementsOnASingleLine: 'false'
+AllowShortLoopsOnASingleLine: 'true'
+AlwaysBreakAfterDefinitionReturnType: All
+AlwaysBreakAfterReturnType: All
+AlwaysBreakTemplateDeclarations: 'Yes'
+BinPackArguments: 'false'
+BinPackParameters: 'false'
+BreakBeforeBinaryOperators: None
+BreakBeforeBraces: Mozilla
+ColumnLimit: '100'
+ConstructorInitializerAllOnOneLineOrOnePerLine: 'true'
+Cpp11BracedListStyle: 'true'
+FixNamespaceComments: 'true'
+IndentWidth: '2'
+PointerAlignment: Left
+ReflowComments: 'true'
+SortIncludes: 'true'
+SortUsingDeclarations: 'true'
+SpaceAfterTemplateKeyword: 'true'
+SpaceBeforeAssignmentOperators: 'true'
+SpaceBeforeCpp11BracedList: 'false'
+SpaceBeforeInheritanceColon: 'true'
+SpaceBeforeParens: ControlStatements
+SpaceBeforeRangeBasedForLoopColon: 'true'
+SpacesInParentheses: 'false'
+SpacesInSquareBrackets: 'false'
+Standard: Auto
+
+...

packages/.clang-format

+---
+Language: Cpp
+DisableFormat: true
+SortIncludes: false
+---
+