doc: describe onlynet option in doc/tor.md

as per http://www.erisian.com.au/bitcoin-core-dev/log-2019-04-11.html#l-102.

Description adapted from https://github.com/bitcoin/bitcoin/blob/master/src/init.cpp#L429.

Also fixes a typo in doc/dependencies.md.

doc/dependencies.md

@@ -43,4 +43,4 @@ Some dependencies are not needed in all configurations. The following are some f
 * ZeroMQ is needed only with the `--with-zmq` option.
 
 #### Other
-* librsvg is only needed if you need to run `make deploy` on (cross-compliation to) macOS.
+* librsvg is only needed if you need to run `make deploy` on (cross-compilation to) macOS.