Heavy refactoring, defines, privatized some functions.
New files for posts, user summary, general HTML, and threads.
Add user information cache. This avoids frequent DB calls as a user's info might be needed several times on a single page.
* src/forum/blocks/threads.clj: (view-thread) get user name from cache instead of printing user ID
* src/forum/db.clj: (get-user-info) new function. Retrieves basic user information from DB
* src/forum/user_cache.clj: new file. Cache basic user information for easy retrieval