v2.2
	* Added drop the lowest grades logic
	* small improvements in error messaging (can output location of the caller)
v2.1
	* Access to grades database wrapped in one transaction for speed 
	* Improved and sped up update grades logic
	* Recoverable column deletion
	* there is a way to speed profile code, see ./test_weight_calc.tcl 

v2.0
	* One password database for all classes for all users
	* logger accept human readable message priority level