FEAT #8750 Create and get signatures

rest/index.php

sql/data_fr.sql

sql/structure.sql

src/app/docserver/controllers/DocserverController.php

src/app/docserver/models/DocserverModel.php

src/app/resource/controllers/ResController.php

src/app/resource/controllers/StoreController.php

src/app/resource/models/ResModel.php

src/app/resource/models/ResModelAbstract.php

src/app/user/controllers/UserController.php

src/app/user/models/UserModel.php

src/app/user/models/UserModelAbstract.php

src/app/user/models/UserSignatureModel.php

src/app/user/models/UserSignatureModelAbstract.php

src/core/controllers/PreparedClauseController.php

src/core/models/CurlModel.php