A user can setup associations in topydo config file and then search will
take those associations into account. For example with

	[implied]
	# X implies -> A B C ...
	+pygolang   = +work +python +go
	+wcfs       = +work
	@jp         = +work
	@jerome     = +work +zodbtools
	...

I can associate projects and people to "+work" label, and then use that
label to query for work-related todo and todos not related to work:

	$ t +work	# todo itmes related to work
	$ t -+work	# todo items related to not-work

this provides a bit of start for work/life balance without explictly
marking every todo with redundant +work label or using complex queries.