allowing attribute names which are not valid comp identifiers

There are a lot of datasets available with rather complex attributes names which are not valid comp identifiers. This change allows to access these attributes in the following fashion:

    record["complex attribute name"]

example:

    [ a["my identifiers with spaces"] | a <- inputdata ]

The attributes with names as valid comp identifiers are therefore accessible in two ways:

    [ a.id | a <- inputdata ]

or

    [ a["id"] | a <- inputdata ]