cordova-plugin-purchase plugin issues

[brodycj]

• installation was broken by 7.1.2 release (Issue to copy library from plugin after updating to v7.1.2 #540 (comment), cordova android build error - The "path" argument must be of type string j3k0/cordova-plugin-purchase#756)
• before-plugin-install hook script was needed to support both cordova-android@6 and cordova-android@7 (https://github.com/j3k0/cordova-plugin-purchase/blob/master/scripts/androidBeforeInstall.js#L21-L25, [ANDROID] billing_key_param.xml requested for changes not found j3k0/cordova-plugin-purchase#729, Fix android install on android-studio projects j3k0/cordova-plugin-purchase#734, Error when Reinstall ( IInAppBillingService.aidl already exists! )  j3k0/cordova-plugin-purchase#742, Fix the IInAppBillingService.aidl fix j3k0/cordova-plugin-purchase#747)

Issue with 7.1.2 release seems like it should be solved by PR #539 but I would have to test to be 100% sure.

The before-plugin-install hook seems to be needed to deal with .aidl, changed res location, and maybe changed config-file handling. Using hook scripts is an ugly solution that we would like to avoid, especially considering that they are not supported by PhoneGap Build.

This issue may turn out to be a duplicate, raising it before we lose track.

[brodycj]

Now part of #547, closing as a duplicate