[NEW_FEATURE] Add open session in the new instance and customizable multi-instance feature.
[NEW_FEATURE] Add new command line argument "-openSession" for opening a session file.

git-svn-id: svn://svn.tuxfamily.org/svnroot/notepadplus/repository/trunk@1079 f5eea248-9336-0410-98b8-ebc06183d4e3