Non-Google platform support

[xcolwell]

We need to make some minimal changes to not have a broken experience on non-Google platforms. Collecting items below.

• [ ] "Sign in With Google" should be active when NetworkSpace.SsoGoogle is true. This needs to be added to the bundled network spaces in build.gradle as e.g. BuildConfig.BRINGYOUR_BUNDKE_SSO_GOOGLE.
• [ ] The Google subscription flow should only be active when NetworkSpace.StoreGoogle. This needs to be added to the bundled network spaces in build.gradle e.g. BuildConfig.BRINGYOUR_BUNDKE_STORE_GOOGLE.

Alternate payments and login may be shown on other platforms, e.g.

• https://github.com/bringyour/android/issues/173
• https://github.com/bringyour/android/issues/172

[xcolwell]

@stuartwk collecting items here to fix up the build for Fire, F-Droid, Github direct, and Samsung distributions.