Add command line flags for which windows to show

[RyanJennings1]

Add --help flag and also flags for which windows to show.

gtop [-cpu|-mem|-net|-disk|-proc]
+
+    With no flags supplied gtop runs all on default
+    Adding flags will show only the windows for the flags supplied
+
+    -cpu: Show the cpu usage window
+    -mem: Show the memory usage window
+    -net: Show the network history window
+    -disk: Show the disk usage window
+    -proc: Show the running processes window

But this just turns the windows on or off basically, it doesn't resize the windows sizes it shows a blank box if the window is off. There will be a lot of changes to code and order of functions to correctly resize each window depending on which are selected.

Any feedback?

[pawamoy]

I don't use swap so it would be cool if we were also able to display/hide the swap part.