CnameGenerator takes too much time during class loading

[hrosa]

The Base64 conversion in CnameGenerator can take up to 230ms during class loading.
Replace for the faster DatatypeConverter.

[hrosa]

Class loading times reduced from 200ms to ~10ms during local tests

2016-08-17 18:06:28,488 INFO [org.mobicents.media.server.impl.rtp.CnameGeneratorTest] worker-2 took 8ms to generate the cname qUJ7OOdmOTBCHZZl
2016-08-17 18:06:28,488 INFO [org.mobicents.media.server.impl.rtp.CnameGeneratorTest] worker-1 took 8ms to generate the cname kaGBlQ24Rc4vddvx
2016-08-17 18:06:28,488 INFO [org.mobicents.media.server.impl.rtp.CnameGeneratorTest] worker-3 took 8ms to generate the cname nM/6M2anJXrOpIMK
2016-08-17 18:06:28,660 INFO [org.mobicents.media.server.impl.rtp.CnameGeneratorTest] worker-3 took 1ms to generate the cname oyW/25hhc0iqjQHw
2016-08-17 18:06:28,660 INFO [org.mobicents.media.server.impl.rtp.CnameGeneratorTest] worker-1 took 1ms to generate the cname j4dZPE5N/n9GrFbG
2016-08-17 18:06:28,660 INFO [org.mobicents.media.server.impl.rtp.CnameGeneratorTest] worker-3 took 0ms to generate the cname j1oMsAakVBCMnCnn
2016-08-17 18:06:28,660 INFO [org.mobicents.media.server.impl.rtp.CnameGeneratorTest] worker-2 took 1ms to generate the cname hOCV17GQv8uR6B7o
2016-08-17 18:06:28,660 INFO [org.mobicents.media.server.impl.rtp.CnameGeneratorTest] worker-3 took 0ms to generate the cname jHxR5E+HyAWManE0
2016-08-17 18:06:28,660 INFO [org.mobicents.media.server.impl.rtp.CnameGeneratorTest] worker-1 took 0ms to generate the cname hyt6iiB6ldXmeNGu
2016-08-17 18:06:28,660 INFO [org.mobicents.media.server.impl.rtp.CnameGeneratorTest] worker-2 took 0ms to generate the cname n0OgCvtWvp5jTPQB
2016-08-17 18:06:28,660 INFO [org.mobicents.media.server.impl.rtp.CnameGeneratorTest] worker-3 took 0ms to generate the cname pTyP1TnAI4Hsu1Co
2016-08-17 18:06:28,660 INFO [org.mobicents.media.server.impl.rtp.CnameGeneratorTest] worker-2 took 0ms to generate the cname tTV9GlReB70AKN1Y
2016-08-17 18:06:28,660 INFO [org.mobicents.media.server.impl.rtp.CnameGeneratorTest] worker-1 took 0ms to generate the cname jBMpRqpY3hQurF1V
... and so on