Merge pull request #7 from finnlabs/release/3.0

Release/3.0
Merge branch 'release/3.0' into dev (again)
Merge branch 'release/3.0' into dev
Bump version to corresponding core version
Remove mention of openproject-plugins in README

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Remove superfluous comment in engine.rb

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Merge branch 'release/3.0' into dev

Conflicts:
	lib/open_project/help_link/version.rb
Update stable to v4.0.0