Add logout

[ryanshappell]

Within the header add a logout button to signout a user

[ryanshappell]

Added icon, still need to add the actual logout function and only show the logout button if logged in.

[aaronshappell]

Can use <div sec:authorize="isAuthenticated()"> and <div sec:authorize="isAnonymous()"> to check for authentication. Can also use<div sec:authorize="hasRole('ROLE_USER')"> to check for the USER role or <div sec:authorize="hasRole('ROLE_ADMIN')"> to check for the ADMIN role. Need xmlns:sec="http://www.springframework.org/security/tags"> to use sec:.

[ryanshappell]

Done