Move the edit plugins view logic out of the plugin manager

separation  of concerns.
make the plugin manager a singleton

This allows for more control over how it is initialized and used.
move some logic out of the consturctor, add comments

This logic tries to act on itself, which breaks things because it isn't yet initialized.  So, wait to execute until after the object is constructed.
add the steam id to the user object
correct class vars
use the correct vars
Move redundant logic to parent class

Move logic to get and set vars to parent class to reduce code.
Also, instead of checking for an object property, check if it is a registered field for the table.