Android x migration

[malinajirka]

This PR replaces SupportLibrary with AndroidX.

I simply used the AS migration tool. The only thing I had to do manually was adding androidx namespace to Checkstyle.xml + Project.xml and reorder the imports.

Merge instructions (please cross off completed steps)

1. Wait until Import changes from WPAndroid #18 is merged
2. Wait until issue/glide-4.9  #17 is merged.
3. Merge develop into master-android-x
4. Update the target branch of this PR to master-android-x
5. Test the library in either WPAndroid or WCAndroid - whichever is migrated to AndroidX first. (for WPAndroid git subtree pull --prefix=libs/login git@github.com:wordpress-mobile/WordPress-Login-Flow-Android.git master-android-x --squash)
6. Merge this PR
7. Create a new PR for master-android-x to develop which can be merge when both WPAndroid and WCAndroid are migrated to AndroidX

[malinajirka]

This build is failing due to two reasons

1. We need to update Dagger's version
2. We need to add android.useAndroidX=true, android.enableJetifier=true properties into 'gradle.properties' on CircleCI
   I've tried to assemble an apk after making these changes in it worked as expected.

I'm closing this PR as I think it makes more sense if we perform the migration in the app repo and push the changes here.

Feel free to re-open it if you think we should rather merge the changes here.

[aforcier]

@malinajirka that makes sense.

Do 'the app repo', do you mean WooAndroid or WPAndroid? IIRC the original plan was to do libraries -> WooAndroid -> WPAndroid, so if we want to make the subtree changes inside an app it might work out better to do it from WooAndroid. But as long as a feature branch is used in this repo it's probably fine.

Also, there was an issue updating to Gradle plugin 3.3.+: wordpress-mobile/WordPress-Android#9436. The big blocker was Fabric, which now should be fine as we dropped it, but there was also an issue with the bintray release plugin. I see a version 0.9.1 was recently released, that may have resolved the issue.

[malinajirka]

Do 'the app repo', do you mean WooAndroid or WPAndroid? IIRC the original plan was to do libraries -> WooAndroid -> WPAndroid, so if we want to make the subtree changes inside an app it might work out better to do it from WooAndroid. But as long as a feature branch is used in this repo it's probably fine.

I meant whichever is migrated first:P. But it makes sense to proceed with WooAndroid migration first.

I see a version 0.9.1 was recently released, that may have resolved the issue.

Good point. I'll make sure to test it.