Revert tool symlinks branch

Revert "Merge pull request #360 from scraperwiki/20130816-tool-symlinks"

This reverts commit 5089bffb018cdf2db76f6e0f343effc190889e94, reversing 
changes made to 357ab18bdb7d740e2a3fb51325d4fc7e45a2f4cc.

This broke the magic table scraper, amongst others, because they write to
the tool directory (which they're not able to when it's a symlink to a read
-only file system)

To re-merge when we're ready, this commit should be reverted, and then
the branch can be re-merged with whatever additional changes it has.