Allow IPv6 host addresses

Syntax examples:
  fe80::1111:2222:3333:4444
  user@fe80::1
  user@[::1]:2222 (square brackets are necessary for non-standard ssh port number)
Add IPv6 support for rsync project synchronization
Add some IPv6 related comments
Add test coverage for IPv6 related functions
fix typo
Whitespace
Hide some old test output
Preserve retval of execute()d tasks in base/serial cases

Re #474
More old test output fixes
More tests re #474
Remove debug output
Use exception as return value for skipped-over network errors

Re #474
Fix stupid oops re: parallel mode :(
First draft of parallel+queue for return values

Re #474
Missed a spot re: NetworkError. This isn't auth related.
Changelog/docs re #474
Allow use of Task-but-not-WrappedCallableTask in execute()
Fix to the fix
Merge branch 'master' into 474-execute-return-value

Conflicts:
	tests/test_tasks.py
Mentionning lcd in the tutorial.