make big asks/bids standout in order book

[peterhost]

at last.

[prof7bit]

the idea is good, I'm just not yet ure if I can merge this as it is now because I also have some improvements in mind regarding the display of the orderbook (also grouping of orders and display of summed totals and how this could be combined with my planned depth chart), I'll leave this open for now.

[peterhost]

np. I've sorted my patches (big order standout, oyvind's 'small order ignore' and my 'custom user color in config') in 3 sperate commits on my clone.

I rebase your commits in my repo on a daily basis, so as to keep it updated.