add every output support for agg graph + some agf fixes

[cyanpencil]

Support for the following output formats for agg custom graph:

- non interactive ascii-> blank 
- interactive ascii    -> v     
- tiny ascii           -> t
- graphviz dot         -> d  
- json                 -> j 
- gml                  -> g  
- SDB key-value        -> k 
- r2 commands          -> *  
- web/png              -> w  

NOTE: this pr will change the behaviour of the aggv command: now it is renamed to aggw. (this is because "v" format is for interactive ascii).

I also added some fixes to my previous pr (for the agf output format support), mostly to remove \t tabs in the terminal output.

[radare]

plz rebase

[cyanpencil]

Unfortunately the problem wasn't the rebase...
I think I messed up a free() somewhere. Let me double check

[cyanpencil]

I think I found it, I was doing a double free inside cconfig.c when the "dot " program viewer wasn't on the system, so I never had the segfault locally, but only on travis

[radare]

thanks!