WiP to disable fees for specific accounts

* added new account table column: `no_fee`
* honor `no_fee` flag during payout process
* added upgrade SQL file for this feature

Address #260
Adding No Fee option to admin panel

Admins can disable a users fee via admin panel now.

Fixes #260
Fix some reported issues in #260
Merge pull request #501 from TheSerapher/issue-260

Issue 260