Streaming Doc and M/R-Tutorial Doc - updates

This JIRA addresses issues in the Streaming doc that also require a cross-link to and update in the M/R Tutorial doc. All changes approved by the reviewing engineer.

Streaming issues:

1. During the execution of a streaming job, the names of the "mapred" parameters are transformed. The dots ( . ) become underscores ( _ ).

Docs affected: streaming and m/r tutorial (new sub-sections added under Task Execution & Environment section)

2. For -files and -archives options, Hadoop now creates symlink with same name as file (user-defined symlinks, #mysymlink, currently not supported)

Docs affected:streaming

3. Streaming supports streaming command options and generic command options. Generic options must be placed before streaming options, otherwise command fails.

Docs affected: streaming (reorganized the streaming doc to make distinctions between 2 sets of command options more clear)