Allow to setup reserveDiscCache from Configuration Builder, in cases where default reserveDiscCache is wrong

ReserveDiscCache implementation initialized as default. But some devices not home cache dir, and Contex.getCacheDir() may return null. In this case, we have:
java.lang.IllegalArgumentException: "cacheDir" argument must be not null - when configure UIL.

This add ability to control reserve disc cache from client code, for more accuracy usage.