Various improvements

[khromov]

Hello. We needed a similar plugin for our site so I forked yours and made some improvements.

Since I reformatted the code style to use the WordPress official coding guidelines, this PR might be more readable by excluding the whitespace: https://github.com/jaredatch/Disable-Users/pull/23/files?w=1

Changelog:

= 2.0 =

* Add multisite compatibility
* Add enable/disable links from user lists
* Use better hook for user login checking (supports XML-RPC)
* Add Swedish translation
* Reformat code to WordPress official code style

Multisite was currently not supported properly because it allowed any admin for a single site to disable users across the entire network. This is adressed by only allowing super admins this possibility on multisite.

Screenshot of new UI option:

As for changing how the logged in status is stored (from a string 0 or 1 to a boolean), WP handles it the same way internally so it's backwards compatible.

Let me know if there is anything you want me to change or if you have any questions.