draft of code
[WIP][issue #368] code implemented, and documentation added
[WIP][issue #368] flash statement in code modified
[WIP][issue #368] UML added
[WIP][issue #368] Documentation typo modified
[WIP][issue #368]UML modified
[WIP][issue #368] UML modified
[WIP][issue #368] tests in progress
[WIP][issue #368] tests added
[WIP][issue #368] UML modified, and code cleaned
[MC][issue #368] solving merge conflicts with master
Merge pull request #409 from MGhanem/C2_Omar-Hossam_C5S17_admin-create/remove-categories

C2 omar hossam c5 s17 admin create/remove categories