Add hints about what data goes into the variable

It's not immediately obvious what all can be accessed from the register
variable. Breadcrumbs to use -v would help.
Update wait_for documentation - remove extra quote

The timeout is in seconds (int), and the extra quote at the end could throw someone off if they're copying and pasting the example.
Mention shell module in command documentation

Users who use the command module for pretty much all shell commands may be stymied when they try using a command with <, >, $VAR, etc., and not know that they can use the `shell` module instead. This documentation fix clarifies this.
Added info on --skip-tags to tags documentation.
Fixed typo

Used the twice in a row
Merge pull request #5816 from Czachur/patch-1

Fixed typo
Merge pull request #5784 from geerlingguy/patch-1

Update wait_for documentation - remove extra quote
Merge pull request #5790 from geerlingguy/patch-3

Mention shell module in command documentation
Build variable dictionary on included plays without using dict()

Using dict(k=v) means the key was always named 'k', as the variable
is not interpreted there.

Fixes #5801
Merge pull request #5815 from saltvedt/patch-1

Added info on --skip-tags to tags documentation.
If a executable is defined but not found the module should fail. Addresses https://github.com/ansible/ansible/issues/5781.
Add move_home option to user module
Merge pull request #5821 from risaacson/issue5781

If a executable is defined but not found the module should fail.
Merge branch 'devel' of https://github.com/aclindsa/ansible into aclindsa-devel
Merge pull request #5759 from j2sol/register-hints

Add hints about what data goes into the variable
Micro-optimization of inventory.expand_hosts.detect_range
Micro-optimization: replace s.find(x)!=-1 with x in s

timeit shows a speedup of ~3x on Python 2.7.5 x86_64.
It also makes the code a bit shorter.
hostname module: don't filter hostnamectl with awk

There's no need to filter hostnamectl's output with awk because its man
page says:

    hostnamectl [OPTIONS...] {COMMAND}

       --static, --transient, --pretty
	   If status is used (or no explicit command is given) and one
	   of those fields is given, hostnamectl will print out just
           this selected hostname.

E.g. hostnamectl --static status => ansible.example.org