Remove redundant code

[ZXGuesser]

Purge irrelevant code carried over from editor.

• Page saving is used in commented out debug code in SendSubtitle is this needed, would a simpler page dump suffice for debugging?
• There is code for multiple formats but we only read tti. Do we want to (re)implement loading the other formats or should we throw them out? Affects Support for ETT (.ttp) file format #19

[peterkvt80]

Probably best to drop the irrelevant code. So get rid of page saving and formats other than tti..

[ZXGuesser]

That's chopped out a bunch of dead stuff in 0f6b2bb. There's no doubt more in code that I don't fully understand.
I notice there's duplication of page copying, could this be consolidated? I see that it's used by the subtitle stuff which I've never dug into enough to figure out how it all works.