Add model downloader activity for voice input

build.gradle

java/AndroidManifest.xml

java/res/values/strings-uix.xml

java/src/org/futo/inputmethod/latin/LatinIMELegacy.java

...org/futo/inputmethod/latin/settings/SettingsActivity.java

...org/futo/inputmethod/latin/settings/SettingsFragment.java

...org/futo/inputmethod/latin/setup/SetupWizardActivity.java

...rg/futo/inputmethod/latin/uix/actions/VoiceInputAction.kt

...ethod/latin/uix/voiceinput/downloader/DownloadActivity.kt