Code style

Fixes #4172
Update en-GB.com_templates.ini

Simplify a language string. Fixes #4163
Log clientip Fixes #4158

In logs/error.php missing client IP column.
Wrong JText causes mixed string use. Fixes #4156e
Remove reference to JoomlaCode
Removed wrong default values in the google maps constructor. Fixes #4166
Removing false error_reporting setting in the installer. Fixes #4176
Made the API key optional. Fixes #4167
- email cloaking does not work with special char. Fixes #4182 Thanks @infograf768
Com_contact default form code style improvements. Closes 4072
[imp] Make blog intro image link to article. Closes #4134
[imp] Post-Installation Messages extension drop-down. Adding addPostInstallationMessage method. Closes #4180.
Codestyle
[add] JImageFilterBackgroundfill. Closes #4189.
Correct `since` tags.
[add] Add support for PDO based connections for MySQL. Closes #4123
[imp] Sql optimise category edit options branch. Fixes #4106
[imp] Repeatable form fields. Fixes #3574
Merge remote-tracking branch 'joomla/staging' into 3.4-dev
Merge remote-tracking branch 'joomla/3.4-dev' into 3.4-dev