Merge pull request #85 from Gaerzi/master

Sync with my fork.
Update README.md

Added some links.
Merge pull request #86 from Gaerzi/master

Added res folder validator.
Update README.md
Added icons to recent file lists (archive manager panel, recent files menu and start page)
Merge branch 'master' of https://github.com/sirjuddington/SLADE.git