Introduce Guild System

Work in progress.

- [x] Display guild informations tab.
- [x] Display guild members tab.
- [x] Display guild positions tab.
- [ ] Display guild skills.
- [x] Display guild leave history.
- [x] Display guild notice.
- [ ] Able to create a guild using UI.
- [x] Able to create a guild using /guild command.
- [x] Able to disband guild using /breakguild command.
- [x] Able to invite player using context menu.
- [x] Able to set a guild as ally/antagonist.
- [x] Able to view/delete ally/antagonist guild in guild info tab.
- [x] Display guild emblem in guild info tab.
- [ ] Render graphic tendency in guild info tab (is it even used ?).
- [x] Able to leave a member from guild member tab.
- [x] Able to expel a member from guild member tab.
- [x] Display members head in guild member tab.
- [ ] Able to change member position from guild member tab.
- [x] Able to edit positions in guild member positions (title, tax, rights).
- [ ] Able to use guild skills from guild skills tab.
- [ ] Able to level up guild skills from guild skill tab.
- [x] Able to modify guild notice.
- [x] Display emblem in entity's display (mouseover).
- [ ] Able to add/change emblem (require a deflate algorithm).
- [ ] Some tabs can be display but not edit (currently can't click on them).
- [ ] Contextmenu on entity's should check if it has a guild, if it's on our guild, etc.