Update native projects

[Arrnas]

Retry of #5, had a number of issues doing this:

• project won't compile on xcode 10 without using legacy build system
• react-native-git-upgrade would fail solving conflicts and abort
• mobx v5 won't work on android unless we upgrade native javascriptcore or downgrade to mobx v4: Can't find variable: Symbol mobxjs/mobx-react#498 (comment)

Managed to successfully launch on ios and android.

[Arrnas]

decide to downgrade mobx instead of upgrading javascriptcore in android native project as it require bumping min sdk version

[shroomist]

have you tried this?
mobxjs/mobx-react#498 (comment)

[Arrnas]

@shroomist saw it as an option but didn't want to mess with android native dependency and the change requires setting the minimum android SDK version to 21.. Having said that I don't know about the drawbacks of using mobx v4 vs v5, do you think it would be worth it to use v5?

[shroomist]

recently I've came across Symbols usage several times in different libs.
in our codebase we're increasingly using features from future JS proposals via babel.

this one seems like it's some default value, that's been left behind, not updated at react-native project.
I'm wondering, what's the down side of using the newer version of sdk 21 vs 16?
are we dropping support for legacy devies?

@donce might also have an opinion here

[Arrnas]

sdk 21 is Android 5.0 (LOLLIPOP) and according to this usage bellow that is ~18% while usage bellow sdk 16 is ~2% ¯\(ツ)/¯

[shroomist]

in that case we're dropping support for jellybean up to lollipop, which are no longer maintained and together <8% of devices as of february 2018.
I'd rather drop those and have a more up to date environment.

[donce]

Since this fixed master builds for android, I fully approve it :) We can decide later whether we need new features for MobX or not - we're not using them ATM.

[shroomist]

I will be eager to bump the sdk versions later on ;D