hledger-ui; add < CR > and < SHIFT >< CR > as navigation keys

[linuxcaffe]

For me, the most natural/ common thing is navigating by selecting with cursor keys and "drilling down", or following a link, with a < CR >. I was surprised to see that hledger-ui doesn't seem to use the enter-key at all, so thing request is to add these keys as basic navigation;

RIGHT/l/CR more detail LEFT/h/SHIFT-CR previous screen

[simonmichael]

I took it out in order to free up CR for something... in-place edit ? some funky navigation on the transaction screen? maybe the commit message knows more.