Clean up the Japanese language initialisation somewhat

Instead of init functions we use class constructors to set up the
necessary fields.

Additionally, we avoid using a single-element ArrayList in the tag
function to build new AnalyzedTokenReadings by simply passing the
AnalyzedToken directly to the constructor of AnalyzedTokenReadings.
Merge pull request #172 from Shugyousha/japaneseinitV2

[ja] Clean up the Japanese language initialisation somewhat