Added new forum feature

[yapxinyee]

• Added forum buttons in the homepage (index.html).
• Created database (connectDB.php); Run this before go for the forum page. (using Wampserver)
• Added pastel-background.jpg as the background in the forum page.
• Created forum.php for display the table of posts.
• Created write-form.html for user write new post in the forum.
• Created writeDB.php for update the post details into the database.
• Created reply-form.php for user to reply the post in the forum.
• Created replyDB.php for update the reply details into the forum.
• Created forum-style.css for styling write-form.html and reply-form.php.