[WIP] My account section : home, profile edition and password change

This PR refers to the following discussion : https://github.com/Sylius/Sylius/issues/88
A RFC describes the features and the implementation here : https://github.com/Sylius/Sylius/wiki/%5BRFC%5D-My-account-section

Two features of the __my account__ section will be released with this PR : 
* profile edition
* password change