Previously we assumed the shell on the target systems were 'sh'-
compliant when formatting environment variables preceding command
strings. This patch corrects that by basing the target shell type
on the DEFAULT_EXECUTABLE setting, which can be overridden on a
per-host basis using the inventory variable 'ansible_shell_type'.

Fixes #7352

rules are avaialble at https://en.wikipedia.org/wiki/Wikipedia:AutoWikiBrowser/Typos

- extra 'the' in intro_inventory
- capitalization in playbooks_roles

Reference #7102

Merges the functionality of the original jinja2 random filter with
the one we provide.

Fixes #7113

Moved a sentence. Sentence refers to script, "this particular script" before it has been introduced. Moved sentence to after intro as it confused me. I though I'd missed something..

Document that roles_path can support multiple colon-separated paths

This group is useful when using multiple inventory sources.

Fixes #6692

timeit shows a speedup of ~3x on Python 2.7.5 x86_64.
It also makes the code a bit shorter.