WordPress Compatibility Release - Tested up to 3.9.1

WordPress compatibility bug fixes and installation method changed. Now this plugin has its own option page "**PMC Lockdown**" under Settings.

**Please Note**
*Legacy plugin option will work without any issue, so updating plugin will take the option value from the existing old plugin setting.*

**muplugins_loaded** changed to **plugins_loaded**

The plugin has its own options page; this improves flexibility for adding and customizing plugins for more options. 
> By doing the above changes, the plugin can adapt more features like below:

Further improvements:
* Comments disabled and admin logout options can be separated
* With the new option page, it is now more easy to add more options into the plugin. We can add more specific wordpress sections to enable disable. 
* There can be many other features added to the plugin eventually, like:
* Block/Unblock Subscribers/Authors/ or specific users from the lockdown settings page
* Disable / Enable search function of the site
* The above set of features will be very useful for the site owners who wants to minimize the site load during the critical updates to the system. The whole purpose of this plugin to disable writes to the database and allow users to read the content. 
* readme.txt updated.