rename 'app-id' to standard Android 'applicationId'

* https://developer.android.com/studio/build/application-id.html
* https://sites.google.com/a/android.com/tools/tech-docs/new-build-system/applicationid-vs-packagename

This only changes the term in the human texts, not var names or CLI flags.
2 jobs for implement-gettext in 42 minutes and 12 seconds
Status Job ID Name Coverage
  Test
passed #32769386
metadata_v0

00:03:13

passed #32769385
test

00:42:12