bump themis iOS to 0.12.2, update podspec, update examples

[vixentael]

(as part of 0.12.0 release flow)

Due to problems with latest GRKOpenSSLFramework 2.19 release I've downgraded dependency to 2.18, pushed new themis.podspec and updated examples.

Unfortunately, 2.19 release doesn't have some symbols and causes failure of archiving Xcode app, see #538.

Good thing:

• it's fixed

Bad thing:

• this fix is temporary until GRKOpenSSLFramework is fixed
• such cruel dependency linking might cause dependency linking failure for projects that use GRKOpenSSLFramework separately.

[ilammy]

such cruel dependency linking might cause dependency linking failure for projects that use GRKOpenSSLFramework separately

Aren’t projects that use GRKOpenSSL independently going to fail to archive even without Themis if they are using the broken 1.0.2.19 version? I guess by pinning the version we ‘fix' the linkage issue for them as well.

Though, it’s still true that dependency resolution might fail if the pinned version is incompatible with other requirements imposed by the project or other dependencies.

[ilammy]

I guess it’s okay to leave Carthage examples using 0.12.1 since 0.12.2 is not any different for Carthage.

[vixentael]

Aren’t projects that use GRKOpenSSL independently going to fail to archive even without Themis if they are using the broken 1.0.2.19 version?

Can't tell now, need investigation. From my first try (see T1326), looks like projects that link GRKOpenSSL directly are being archived ok, projects that use themis->GRKOpenSSL produce error during archiving.