Scott S30 road bike 11speed with 10 speed compatibility I have a Scott S30 bike currently running a shimano 105 2x10 speed 50-34 crankset, shimano 105 10 speed front shifter and 10 speed cassete and chain.
I have a new crank that i want to install, the shimano 105 5800 53-39 but it is 11 speed. I'd like to know if i can make it work with the rest of the bike. I will change cassete and chain anyways because they already need replacement. 
So i have some questions:


Can i buy the same 10 speed cassette i used before? 
I use a 12-25 cassete now, can i upgrade to a 11-28 one or does this require a special rear derailleur?
The chain can be the same 10 speed chain or should i buy a 11 speed one? I have read mixed opinions on this. Some say its fine with 10 speed other say its better with 11...
Are this good cables for my bike? I need to replace them but i can't spend much http://www.bike24.com/1.php?content=8;navigation=2;product=21934
New 105 5800 crankset is compatible with older components, according to numerous posts in this thread.


Yes, you can use the same cassette.
Even if you use short cage rear derailleur now, it should have enough capacity for 28 teeth sprocket.
11 speed Shimano chains have the same internal width, so these should be compatible with older 10 speed systems. Given that you have limited budget, 10s might be a better choice.
Yes, that cable set will be fine.