Change 'standard' analyzer to use empty stopword list by default.

The 'default' / 'standard' analyzer can be a trappy default sicne it filters
english stopwords by default. Yet a default should not be dedicated to a certain language
since elasticsearch is used in many different scenarios where a standard analysis chain
with specialization to english full-text might be rather counter productive.

This commit changes the 'standard' analyzer to use an empty stopword list for indices
that are created from 1.0.0.Beta1 version onwards but will maintain backwards compatibiliy
for older indices.

Closes #3775