Add a location column that displays location of code snippet/issue

[SteveJonesDev]

For the first iteration of this feature, identify the_content, and not the-content. We'll later assess the feasibility of identifying other landmarks such as header, footer, content, widgets, other.

• Create a custom database column to store the issues' location
• Identify the_content and not the_content in the PHP and JavaScript rules
• Create custom user capability and apply it to the appropriate user role.
• Update logic throughout the plugin to not output global (not the_content) issues for the users with the new capability
• Add a location column to the details panel for users that can see all issues

Related: #58

[SteveJonesDev]

Move to Basecamp