Add an option to write tiles to the standard output in tar format

[e-n-f]

For #675

[joustrich]

@e-n-f any chance this could be merged?

[e-n-f]

Although maybe it could just go on writing, and the output files with reduced features would just clobber the files that were written earlier in the stream.

I still hesitate to complicate the output options further. What is your intended use for the feature?

[francois-baptiste]

What is your intended use for the feature?

In my case I use it to circumvent inode limit on my managed webhosting in conjonction with archivemout!