!! describe all the changes made to program source files to help bugs investigation
!! recommend http://www.gnu.org/prep/standards/html_node/Change-Logs.html#Change-Logs

2012-05-01, Bin Gao
	* reorganize the code: by putting recurrence relations of different operators
	into different subdirectories.
	* start to implement the interface using C language

2011-02-04, Bin Gao
	* replace GNU automake with CMake

2010-10-04, Bin Gao

	* new Version 0.2.1: rewrite the code to keep the FORTRAN part simple, while
	providing Python interface; rewrite the recurrence relations by replacing
	the recursive functions; implement the evaluation of integrals with (rotational)
	London atomic-orbital at zero fields.

2009-09-30, Bin Gao

	* fix the bug in subroutine herm_to_cart: the correct transformation between
	Cartesian and Hermite Gaussians is now implemented in gen1int_calc.F90, inside
	the calculation part due to the efficiency; we may write an individual
	transformation subroutine later if it is efficient.

2009-09-27, Bin Gao

	* add magnetic derivatives of London atomic-orbitals.

2009-09-21, Bin Gao

	* add module "gen1int_derv": takes care the derivatives.

2009-09-09, Bin Gao

	* add type "g1int1": defines the integrals belong to a property.

2009-09-27, Bin Gao

	* add subroutine to get AO density matrices (restricted) and calculate expectation values.
	* allow the center of multipole moments always being the center of ket:
	useful, for example, for "ANGLON".

2009-09-04, Bin Gao

	* fix the bug for calculating derivatives (gen1int_calc.F90):
	we need to explicitly consider what the derivatives will act,
	the center of bra, ket, r function or multipole moments, using
	product rule in calculus and translation invariance.

2009-08-26, Bin Gao

	* change the operators of property integral as one-dimensional array:
	which is more convenient to sum over operators, like property integrals
	*THETA and *NSTCGO.

2009-08-24, Bin Gao

	* adopt new auxiliary function \int_0^1\exp(-T(1-u^2))u^{2n}du for operator 1/r_C^2:
	which requires different recursion relations for calculating integrals.

2009-08-17, Bin Gao

	* three major updates of the definition of operators: it becomes easier and
	more efficient to compute geometric derivatives of any property integrals to any order

2009-06-13, Bin Gao

	* add a unified interface gen1int_basis_get to get basis sets:
	which will call other low level subroutines to get basis sets.
	* add clause to get charges of atoms:
	which are need for some integrals.

2009-06-12, Bin Gao

	* add module gen1int_input to process input information
	* use type structure for the generalized one-electron integer:
	module gen1int_operator will handle the operator.

2009-06-11, Bin Gao

	* add subroutine gen1int_basis_dalton: reads basis set from DALTON common blocks.

2009-06-10, Bin Gao

	* add subroutine gen1int_basis_q5cost: reads basis set from Q5Cost.

2009-05-21, Bin Gao

	* add subroutine: to evaulate the auxiliary funtion when using operator 1/r^2.

2009-05-07, Bin Gao

	* implement recursive function: to calculate integral using HG scheme without 1/r^m.

