Change a term in French localization

Most applications, including Apple’s, use « Présentation » as menu title.
Workaround for issue #288

Subclass NSWindow, and apply techniques found at <http://lists.apple.com/archives/cocoa-dev/2008/Jun/msg01216.html> and <http://www.theregister.co.uk/2009/04/29/mac_secrets_framework/>
Silence warnings
Remove inoperative strings

As we handle this programmatically, don’t mislead translators.
Small housekeeping
Merge pull request #304 from barijaona/topic/ShowToolbar

Solve issue #288 (localization of hide toolbar/show toolbar menu item)