[NEW] Add swap line function.

git-svn-id: svn://svn.tuxfamily.org/svnroot/notepadplus/repository/trunk@1147 f5eea248-9336-0410-98b8-ebc06183d4e3
[NEW_FEATURE] Add line sorting feature (in progress).

git-svn-id: svn://svn.tuxfamily.org/svnroot/notepadplus/repository/trunk@1148 f5eea248-9336-0410-98b8-ebc06183d4e3