lib/standard/ropes: Removed ropes.nit from standard library

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
lib/standard/ropes: Rewriting of ropes base block.

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
lib/ropes: Added buffered variant of Ropes.

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
benchmarks/strings: Adapted for new Ropes.

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
lib/standard/ropes: Rope is now an abstract superclass, specialized by RopeString

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
lib/standard/ropes: Introducing RopeBuffer, a mutable `Rope` optimized for concatenations.

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
benchmarks: Adapted bench scripts for RopeBuffers

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
tests: Updated tests for RopeBuffer

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>