Logex

* fix: return value of decorated function was not passed to caller

* fix exception when generating locals view, i.e. if repr(local_variable)
crashes
* add a wrapper function that allows to use logex with sys.excepthook

* whew! many changes ;)
* removed LINE_NUMBERS parameter => always show line numbers when showing
source
* always show locals when showing source
* when showing source, show source for all relevant frames
* shorten source view if one decorated function calls another
* added some examples
* handle our own exceptions, i.e. during generation of the log message
* fix default values for parameters

* initial release