pseudo elements: remove debug message
Documentation::eval: fix formatting ( || operator)
Parse Eval: support unary operations + fix operation 'not'
Eval::not: bugfix, use param to check for input not undefined value
pgmapcss v0.5.1 release
Merge branch 'branch-0.5'

Conflicts:
	pgmapcss/version.py
Merge branch 'master' into HEAD

Conflicts:
	pgmapcss/db/eval/eval_not.sql
	pgmapcss/db/eval/functions.py
	pgmapcss/parser/parse_eval.py