Implement changing focus via keyboard between floating clients, fix several floating bugs

src/table.c

@@ -43,6 +43,7 @@ void init_table() {
         for (int i = 0; i < 10; i++) {
                 workspaces[i].screen = NULL;
                 workspaces[i].num = i;
+                TAILQ_INIT(&(workspaces[i].floating_clients));
                 expand_table_cols(&(workspaces[i]));
                 expand_table_rows(&(workspaces[i]));
         }