Initial TaskManager class and make room for Swap

Added the TaskManager class to hold system information and tasks.
Currently it provides username and hostname based on POSIX functions.
The Swap is now part of the system information and is being displayed in
the statusbar.

src/Makefile.am

@@ -19,6 +19,7 @@ xfce4_taskmanager_SOURCES =						\
 	process-window.c		process-window.h		\
 	process-tree-view.c		process-tree-view.h		\
 	process-statusbar.c		process-statusbar.h		\
+	task-manager.c			task-manager.h			\
 	settings.c			settings.h			\
 	$(NULL)