Improve top level documentation for building releases
Keep word filter through an error if `keep_word_path` was specified.

Closes #4073
Added simplified range syntax to query string docs
Remove Index Reader warmer introduced in 0.90.6
It create the following challenges:
- it automatically load all the norms for all fields. This should be an opt in feature similar to the new loading feature in field data. Will open a separate issue for it.
- It automatically loads all doc values for all fields (if they have it), overriding effectively the loading option of field data when its backed by doc values.

closes #4078
[DOCS] Added documentation for the keep word token filter