Added several methods to JPhonemiser.java.

This pull request adds the following methods:
* dictLookup(): lookup in just one dictionary;
* phonemiseLookupOnly(): lookup in a sequence of dictionaries and with
                         some text normalisation as well.
* phonemiseComplete(): lookup in a sequence of dictionaries, with text
  		       normalisation and letter to sound.

The original purpose of these methods was to allow the support for per-request dictionaries, but I think they are useful in the general case: dictLookup() can be used to perform lookup in any given dictionary (passed as an argument); phonemiseLookupOnly() allows to perform only the lookup part, of the phonemise method, without LTS; phonemiseComplete() allows the usage of a dictionary passed at runtime, so that per-request dictionaries can be used.