Fix OS X Dock Icon and Address Bar title.
Better handling being launched from within a directory with spaces in it.

Change-Id: Ia79f892921f0b947b92efe06b2c67bbb4fb584f1
Reviewed-on: http://gerrit.dmdirc.com/3070
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>