Update setup repositories documentation

Update doc so
http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/setup-repositories.html
example is going to 1.1 instead of 0.90
Fix typo
Version types `EXTERNAL` & `EXTERNAL_GTE` test for version equality in read operation & disallow them in the Update API

Separate version check logic for reads and writes for all version types, which allows different behavior in these cases.
Change `VersionType.EXTERNAL` & `VersionType.EXTERNAL_GTE` to behave the same as `VersionType.INTERNAL` for read operations.
The previous behavior was fit for writes but is useless in reads.

This commit also makes the usage of `EXTERNAL` & `EXTERNAL_GTE` in the update api raise a validation error as it make cause data to
be lost.

Closes #5663 , Closes #5661, Closes #5929
Disable dynamic scripting by default

Closes #5853