add ability to specify output path

[miraculixx]

now accepts options to specify the output path:

# output to path/to/res/icon
$ cordova-splash -p path/to/res -i icon  

To improve compabitility with cordova icons, the default output path is now config/res. Note this breaks backwards compatibility. The --compat switch preserves the previous behavior, i.e. uses the respective platforms path.

[ivywireline]

This is an excellent idea. Please consider merging this in once the merge conflicts are resolved. @AlexDisler