Allow the specification of the installation strategy

[fabiopelosin]

The Podfile should support the following syntax:

integration_strategy = :none
integration_strategy = :frameworks
integration_strategy = :static_libraries

This would allow to support different integration strategies and easy phase in experimental support for new ones. It would also replace the --no-integrate of pod install.

This would greatly simplify the different target scenarios discusse in CocoaPods/CocoaPods#2272

[kylef]

@neonichu Seems to have implemented this differently via 8816eb5 (use_frameworks!).

[segiddins]

So all we need to add after this is a do_not_integrate flag?

[orta]

This is a better answer to the problem IMO, there's still time to change before a public release.

[neonichu]

One issue I see with this is that the user can opt into using frameworks per target, but not doing any integration doesn't really make sense on a target level.

[segiddins]

@neonichu agree, so we just make do_not_integrate be a top-level DSL flag.