Improve New Window performance when the tree view is enabled, to
	partially address bug 4922 (Opening new windows is really slow
	when the tree view is enabled). This affects only the New Window
	case, not the initial window. Here's some timings before and after
	on my laptop with a bunch of stuff expanded (times in seconds):

	                          First window    New window
	Tree View Off                  8              5
	w/ Tree Before My Change      16              37
	w/ Tree After My Change       16	      20

	I made this change by altering tree view semantics slightly. The
	tree view used to do a force reload any time it expanded a
	directory. Now it does a normal load the first time any given
	directory is expanded (as at startup, or when you first expand the
	node), but a force reload on subsequent collapse and
	expansion. This is more in line with the way the rest of Nautilus
	works.

	* components/tree/nautilus-tree-expansion-state.h,
	components/tree/nautilus-tree-expansion-state.c:
	(nautilus_tree_expansion_state_was_ever_expanded): New function to
	see if a node was ever expanded. Being initially expanded does not
	count; only being expanded through an API call to
	`nautilus_tree_expansion_state_expand_node' does.
	(nautilus_tree_expansion_state_load_foreach_callback,
	nautilus_tree_expansion_state_initialize,
	nautilus_tree_expansion_state_destroy,
	nautilus_tree_expansion_state_expand_node_internal,
	nautilus_tree_expansion_state_expand_node): Adjusted to track
	"was_ever_expanded" property right.

	* components/tree/nautilus-tree-model.h,
	components/tree/nautilus-tree-model.c
	(nautilus_tree_model_monitor_node): Add force_reload parameter.
	(nautilus_tree_model_node_begin_monitoring_no_connect): New helper
	function.
	(nautilus_tree_model_node_begin_monitoring,
	nautilus_tree_model_node_end_monitoring): Slightly adjusted helper
	functions.

	* components/tree/nautilus-tree-view.c:
	(filtering_changed_callback): Do a reload of the whole tree, but
	not a force reload.
	(expand_uri_sequence_and_select_end): Simplify logic a bit.
	(expand_node_for_file): Force reload only if this node has been
	expanded before.
	(reload_model_node, reload_model_node_recursive,
	reload_whole_tree): Make force reload an option.