Output redirection

[mattirn]

Command output redirection to variable and file.

Example:

 % ./build repl 
JLine terminal: xterm-256color                             
groovy-repl> # redirect to variable 
groovy-repl> resp=widget -la
groovy-repl> resp.split('\n').findAll{it=~/accept/}
.accept-and-hold
.accept-and-infer-next-history
.accept-line
.accept-line-and-down-history
_tailtip-accept-line
accept-and-hold
accept-and-infer-next-history
accept-line
accept-line-and-down-history
groovy-repl> 
groovy-repl> # redirect to file
groovy-repl> show > data.dat
groovy-repl> 
groovy-repl> # append to file
groovy-repl> keymap >> data.dat

[mattirn]

Fixes #509