Enable plurals tags to match android format

[davidec-twinlogix]

I'm using moko-resources in a project where resource files are pulled from an external translation service in android format.
It would be nice that also "plurals" tag is processed along with "plural".

 <plurals name="hours">
        <item quantity="one">%1$s hour</item>
        <item quantity="other">%1$s hours</item>
 </plurals>

 <plural name="weeks">
        <item quantity="one">%1$s week</item>
        <item quantity="other">%1$s weeks</item>
 </plural>

[steviek]

I just ran into the same issue earlier, I thought it wasn't working and didn't realize it was plural instead of plurals until I copy+pasted the example code.

If changing to plurals isn't possible, having the generator throw an exception when you use plurals would be helpful to debug issues

[Alex009]

i think we can add alias for plural in generator.
and maybe we should add warnings in parsing of xml when found unknown tags

[Alex009]

will be available in 0.18.0.
thanks to @asapha