Support running an arbitrary number of selected specs (instead of only a single)

[fcy]

Kiwi can already run a single spec using KW_SPEC environment variable. This could be improved to run any numbers of specs. Maybe with this format:

<file name>:<line number of spec>[,<line number of spec>][;<file name>:<line number of spec>[,<line number of spec>]]

The AppCode guys that suggested this feature in their issue tracker so they can add complete support to Kiwi. I'd love that since I'm a user of both products.

[stepanhruda]

Actually, KW_SPEC is causing problems right now, because it uses atos, which is not available on devices.

Also, atos is considerably slow, it might work for one spec, but figuring out call sites for multiple specs considerably increased testing time when I was testing it.

We'll need to figure out in more detail how to approach this.

[paulz]

To run selected specs we use the following method:

1. Duplicate scheme with test into something like 'Selected Specs'
2. Mark 'Selected Specs' as not Shared
3. Edit new Xcode scheme and in Test action Info tab under Tests expand interested Test target
4. Uncheck some of the specs to exclude them from 'Selected Specs' scheme test run

We usually keep 2 private schemes: 'Single Spec' and 'Selected Specs' as names suggest to run specs faster and focus on failing tests. Our .gitignore has xcuserdata to exclude private schemes.