API and UI miscellaneous changes after code review

[PrabhakarThummalaDOL]

• [x] adminDashboardTemplate: Manage Users menu - add comment to the code
• [x] add helper methods for custom 2FA implementation
• [x] change NewRegistration to UserRegistration
• [x] add enum/flags for LoginLogout activities
• [x] add MiddleName to the database tables where First and Last name columns exist
• [x] add helper method for LoginLogout (code 99).
• [x] add helper method for IsReturningUser updation (custom 2FA implementation)
• [x] add helper method for Deleted/Disable user logging
• [x] rename the custom indexes as IX_TABLENAME_COLUMNNAME
• [x] add detailed comment for the linq "Organizations" problem.