Update to Robolectric 4.12.2

[MGaetan89]

Description

The main change in this PR is the update of Robolectric to version 4.12.2 (the last version to support min SDK 19).
The following changes result from this update:

• Remove the dependency to org.robolectric:shadows-playservices.
• Remove the custom ShadowNetwork shadow, since it is now in Robolectric.
• Update all the robolectric.properties files to use sdk 19 instead of 18.
• Remove obsolete properties and properties set to the default value from robolectric.properties files.

Note: not all tests are passing locally, but I think that they were failing before my changes too. Let me know if I'm wrong and should investigate more.

Checklist

• Code compiles correctly
• All tests passing
• Validate that all example applications compile, run, and work (if applicable)
• Automated Builds completed successfully
• Extended the README, if necessary

[MGaetan89]

@junaidBazaarVoice any chance to have a look at this PR?

[MGaetan89]

@junaidBazaarVoice I've updated my PR with the latest changes from master

[MGaetan89]

Robolectric 4.16 has been released without the shadows-playservices module.
Let me know if I need to make any change to this PR in order to have it merged.