Add basic sandbox documentation
Revert "Add basic sandbox documentation"

This reverts commit 6bfb5a200c2202baa313903c95ced835316b23aa.

The sandbox feature is already documented (see #1430).
Additionally, the documentation added in this commit is misleading:
'runhaskell Setup.hs sandbox CMD' doesn't work.
Update bootstrap.sh.
Merge pull request #1459 from Blaisorblade/topic/testsuite-failures

Test suite: canonicalize binary path before execution