Update intro_installation.rst

bigip_monitor bugfix for check mode

Fixes #7528

This is different wording for using the PPA to install.  I also added the installation of apt-add-repository package which isn't always installed.

(I'm a newbie but while running these I wished whatever style was being used on the docs pages would have let me  cut and paste the commands without having to edit out the $ characters manually....)

* Fixed error messages to be more descriptive
* Removed direct use of subprocess module and replaced it with calls
  to module.run_command
* Changed AZURE_MANAGEMENT_CERT_PATH to be just AZURE_CERT_PATH, which
  matches what is expected by the inventory script

ec2_group: Fix for 500 error when creating new security groups

Fixes case where properties are retrieved for a non existent monitor
which happens in check mode.

Fixes #7505

Fixes #7506

Fixes #7640

Show friendlier error message if nova.ini is not found.

Signed-off-by: Hector Acosta <hector.acosta@gmail.com>

Fix issue with symlink path detection

Update developing_modules.rst

ansible-pull should respect inventory file settings because, say, Python...

Fixes #7627
Fixes #7664

The os.path.isdir() returns True for symlinks that point to directories,
so we also need to check to make sure it's not a symlink too.

Fixes #7657

ansible-pull should respect inventory file settings because, say, Python interpreter path can be non-default on a host

Fixes #7628

Fixes #7592

Fixes #7631

Clarified, remote_user config item does override ansible current user

Fixes #7658

Fixes #7652

made nested lists diff lengths - caused confusion

Fixes #7598

As a relatively-new user to Ansible, the Nested Loop example made me think it was looping through both lists together (`alice` would go with `clientdb`, `bob` with `employeedb`) and not actually nested. I realize now I was just being stupid, but I feel making the example lists different lengths would prevent such confusion in the future.