[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

wps/cabbiev2.128x96x2.wps

@@ -53,4 +53,4 @@
 %s%ac%?id<%id|%?d(1)<%d(1)|%(root%)>>
 %s%ac%?it<%it|%fn>
 %s%ac%?ia<%ia|%?iA<%iA|%?d(2)<%d(2)|%(root%)>>>
-%s%Sx(Next:) %ac%It
+%s%t(300)%Sx(Next:) %ac%It;%s%ac%t(1)%ft(.rockbox/playername.txt)