[General] Refactoring acc. code conventions

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Code conventions as follows:

1.) Always use { } for code blocks 2.) extern functions start with an upper case letter, e.g. GPIOSetPinValue 3.) static functions start with a lower case letter, e.g. doIt(..) 4.) Each "module method" starts with the module its name, e.g. GPIOBlub 5.) Each "module define" starts with the module its name, followed by an underline, all upper case, e.g. "GPIO_BLUB"

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6.) typedefs should start with a lower case letter, and end with _t, e.g. timer_t

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7.) typedefs of structs should be as follows:

typedef struct {
    [...]
} name_t;

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8.) No empty while-loops 9.) switch-case instead of else if

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10.) Comments which are within a code block should be C-style, i.e. // A comment. Comments which describe a method should be /* A function comment */

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11.) No int type in os code. hal/platform.h includes inttypes.h which should always be used.