Removing ICU dependency on iOS and OS X, improved build system

**Removing ICU**
This pull request removes the dependency on ICU on OS X and iOS
The dependency was big, especially when including the data file.
The build time could also be long if the prebuilt binary wasn't fetched.
This pull request will remove the dependency on iOS.

**Prebuilt dependencies not in git any more**
This pull request also improves the build system.
The binaries are not stored in git any more.
Now, it will work properly in most of the case if build is interrupted.

- Work in progress on #664
- Fixed #647
- Fixed #258
- Might help for #463