Better Focusing Model

Previously I was using the InsidePlaylist and InsideSearchView boolean
values which was a very hacky and unscalable way. Instead I am using a
focus map which can be queried to check which view has focus. Also the
Pages Implementation is kind of on hold because it has a lot of problems
for e.g resizing doesn't seem to work as I imagined. I am keeping that
Idea on hold right now.

ui/focus.go

@@ -0,0 +1,21 @@
+package ui
+
+var FocusMap map[string]bool
+
+func GenerateFocusMap() {
+	FocusMap = make(map[string]bool)
+	FocusMap["Playlist"] = true
+	FocusMap["FileBrowser"] = false
+	FocusMap["SearchView"] = false
+}
+
+func HasFocus(s string) bool {
+	return FocusMap[s]
+}
+
+func SetFocus(s string) {
+	for k := range FocusMap {
+		FocusMap[k] = false
+	}
+	FocusMap[s] = true
+}