add whole document serialization via toString(whole=true, compressed=true)

[jankuca]

This makes it possible to serialize the whole document/subtree as a usable valid XML string.

doc.toString() // -> as before, trimmed and indented
doc.toString(true) // -> untrimmed and indented
doc.toString(true, true) // -> untrimmed and unindented
doc.toString(false, true) // -> trimmed and unindented

[daronco]

+1

[nfarina]

Sorry, I don't know how I missed this before, should have merged this forever ago! Thanks for the patch.

[nfarina]

I just pushed some tweaks to this, FYI. Introduced an options style object for these formatting options, and changed the default toString() behavior to be more intuitive.