batSubstring : Added a lot of test + fix explode, tokens, fields and cha...

I have fix some little bugs (on explode, tokens and fields, little index mistakes) 
And in span function, I have change 'str1 != str2' by 'str1 <> str2' to enable (span (substring "foobar" 0 3) (substrinf "foobar" 3 3)) but I don't known if it is a good idea.