lib/standard/string: Added capitalized/capitalize method to String/Buffer

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
nitvm: Introduces a type which represents initial values inside attributes

Signed-off-by: Julien Pagès <julien.projet@gmail.com>
nitvm: Throw an error when trying to read an uninitialized attribute

Signed-off-by: Julien Pagès <julien.projet@gmail.com>
nitvm: Handles isset expression

Signed-off-by: Julien Pagès <julien.projet@gmail.com>
Merge: Capitalize on Strings

Added the capitalized method on String as requested by @Morriar

Pull-Request: #741
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
Reviewed-by: Jean Privat <jean@pryen.org>
Merge: Correct behavior of attribute reading in nitvm

This (small) PR allows the nitvm to pass more tests related to attributes reading.

The first commit introduces a new type and Instance which represent the initial values inside attributes.
In the second commit, the vm now throw the expected error when reading an uninitialized attribute.
The last commit implements ```isset``` expressions in the vm.

So, all tests base_attr*.nit are now corrects in the vm.

Pull-Request: #748
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>