stdlib/strings: Added view on the chars of String and Buffer class to abstract them from the Collection model

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
stdlib/strings: Removed from_substring constructor (replaced by with_infos)

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
stdlib/strings: Removed usage of Strings as SequenceRead by using chars.

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
stdlib/strings: Temporary removal of Ropes from stdlib.

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
Merge remote-tracking branch 'lucas/string_integration'

Part of String refactor, adds a new "chars" method on strings, should be
preferred to the old way of calling Collection services on Strings and
Buffers.