[Feature] Skin engine Themes grab text from a file %ft(file, line) WIP

allow the skin engine to read text files and return a particular line

you then can use ss on that string to allow display of strings from the file
(Playername comes to mind)

able to be used as conditional
%?ft(filename)<Found|Not Found>

if (selected) line of file is empty the tag is treated as #COMMENT

scroll timeouts now persist thru trackchange

bugfix:
%t(n)%?x<text|text>
would ignore the specified timeout defaulting to 2 seconds

playername.txt generated at boot if it doesn't exist contents: 'RockBox!'

Change-Id: I961910e01be052ef902f77e6d92fc3e367ffe9d0

apps/main.c

@@ -199,6 +199,20 @@ int main(void)
     }
 #endif
 
+#if !defined(BOOTLOADER)
+    char buf[MAX_PATH / 2];
+    path_append(buf, root_realpath(),ROCKBOX_DIR"/playername.txt", sizeof(buf));
+    if (!file_exists(buf))
+    {
+        int fd = open(buf, O_CREAT|O_WRONLY|O_TRUNC, 0666);
+        if(fd >= 0)
+        {
+            fdprintf(fd, "RockBox!");
+            close(fd);
+        }
+    }
+#endif
+
 #ifdef AUTOROCK
     {
         char filename[MAX_PATH];