#365 Removed icons from core that are no longer in use

Deleted icons
- drupalicon.png
- forum-icons.png
Issue #377: Fixes URL path bug introduced in #357.
Issue #367: Added 'Cancel' link to Comment forms.
Issue #367: Added extra path conditions for Comments.
Merge pull request #498 from BWPanda/377/fix_path_bug

Issue #377: Fixes URL path bug introduced in #357.
Merge pull request #497 from dgoutam/#365-remove-unused-icons-from-core

Issue #365: Removed icons from core that are no longer in use.
Issue #375: Fixing links to handbook.
Issue #86: Introducing Layout module, providing multiple site-wide layouts, contexts, and individual block settings.
Merge pull request #483 from quicksketch/86/layout_pr

Issue #86: Introducing Layout module, providing multiple site-wide layouts, contexts, and individual block settings.
Merge pull request #499 from BWPanda/367/cancel_link_for_comments

Issue #367: Added 'Cancel' link to Comment forms.