Using the apklib dependency's folder and not the project's folder when appending the manifest and apklib's dependencies.
Only supplying a single assets folder argument to aapt.
This is achieved by merging all assets into a single combined-assets folder for each artifact that we need to invoke aapt for.
Defined PullParameter#defaultValue as []

This allows to declare empty strings as default values: {""}; additional
checks occurs @runtime
inject MojoExecution
Use ExpressionEvaluator in ConfigHandler to get default values
get the default value of proguard outputDirectory from @PullParameter
Skip proguard execution if the configuration file is missing; it allows
to set android.proguard.skip=false, but only project having a
configuration file will be obfuscated
Give info about reasons of skipping Proguard.
Merge pull request #259 from pa314159/pull/config-handler

config handler improvments
Including transitive aar and apklib deps when generating R for an apklib dep.
Eg apk -> apklib1 -> apklib2 -> apklib3.
When generating R for apklib1 we need to include both apklib2 and apklib3.
Removing unused extractedDependenciesRes folder.
Renaming unpack\libs to unpacked-libs (it doesn't need that level of depth).
Merge pull request #260 from william-ferguson-au/aar-consumption-5

Aar consumption 5