simplify
made LArray.info() nicer in an interactive session

it now returns a ReprObject, which returns itself when going through repr()
interactive session does print(repr(x)) if info returns a string, it displays the repr of the string, which is ugly
fix tests and simplify ReprObject
made info a property
usused code
summarize each line in str(LA) if necessary
always display "dimension" columns
fix str() for 1d arrays
implemented __getitem__ with ValueGroups at any position

we know which axis the ValueGroup correspond to