Remove custom greek/russian charsets encoding

In Solr 1.4, we deprecated support for 'custom encodings embedded inside unicode'.

This is where the analyzer in lucene itself did encoding conversions, its better to just let
analyzers be analyzers, and leave encoding conversion to Java.

In order to move to Lucene 3.x, we need to remove this deprecated support, and instead
issue an error in the factories if you try to do this (instead of a warning).