util: Redefine method for random number generation

The previous definitions random::generateWord* now generate
(cryptographically) "non-secure" random numbers from uniform
distribution using Boost.Random routines.  When (cryptographically)
secure random numbers are necessary, random::generateSecureWord*
routines should be used instead.

Change-Id: I52561119f7e558b4cfe0d250ca8a89e550d21b5f
Refs: #1760