How to add the plugin to the Ionic Crosswalk project using Ionic CLI?

I'm trying to add the plugin to my Ionic Crosswalk project using the following command:

plugman install --platform android --project . --plugin https://github.com/Telerik-Verified-Plugins/InAppPurchase --variable BILLING_KEY="aslfhsjkfhalkshfakhgfkhgkjgh"

I see that appropriate folder with plugin is created in ./plugin folder, but when I try to build an .apk file by using following command:

ionic build android

I see that plugin was not included to the package and of course the application says that it cannot find the plugin file.

Failed to load resource: net::ERR_FILE_NOT_FOUND file:///android_asset/www/plugins/cc.fovea.cordova.purchase/www/store-android.js

I guess that is because the /plugin folder is one level up then /www/plugins folder, which should contain plugins. The structure is like this:

..
/cordova
/engine
/hooks
/platforms
/plugins  <-  plugman installs plugins in this folder
/res
/resources
/scss
/src
/www  <- my project is here and app tries to find any plugin in /www/plugins
.bowerrc
.gitignore
bower.json
config.xml
gulpfile.js
ionic.project
package.json

But the application tries to find the plugin in the folder /www/plugins I don't know how to set the proper path to the plugin folder or how to force plugin installer to install plugins to the /www/plugins folder, and make ionic to include this folder to .apk file. The same problem with any other plugin.

Does anybody face the same problem?