Make sure options are specific to each plugin.

So this feels like a contentious decision.  It'd be awesome to have the
options for the methods stored along-side the methods themselves.

The downside with this is that the thing accessing the configuration
data is always the plugin, so it's the plugin that must have requested
the configuration option.  This is also important in case the
description of the configuration option needs modifying for clarity or
providing context for how it will be used.

If the interface changes, all plugins calling the plugin methods will
need updating, so the config options can be updated if necessary.

volatility/framework/plugins/windows/dlldump.py

@@ -52,7 +52,11 @@ class DllDump(interfaces_plugins.PluginInterface):
                                             description = "Process virtual memory address to include " \
                                                           "(all other address ranges are excluded). This must be " \
                                                           "a base address, not an address within the desired range.",
-                                            optional = True)] + pslist.PsList.list_processes_filter_requirements
+                                            optional = True),
+                requirements.IntRequirement(
+                    name = 'pid', description = "Process ID to include (all other processes are excluded)",
+                    optional = True)
+                ]
 
     def _generator(self, procs):
         pe_table_name = intermed.IntermediateSymbolTable.create(