Bug 1061801 - profile.sh should support symbol.api.

The "-s" option now accepts an url, which tells that we want to use a
symbol server API for symbols resolution.
Optionally source $DEVICE_DIR/flash.sh for per-device flashing commands.
Merge pull request #390 from cgjones/per-device-flash

Optionally source $DEVICE_DIR/flash.sh for per-device flashing commands.
Merge pull request #389 from walac/bug-1061801

Bug 1061801 - profile.sh should support symbol.api.