major revision on the handling of tunneling out current density boundary condition

- ENH : normalize the tunneling out probability in terms of the electron density at the tunneling-out boundary
- NEW :  use implicit scheme to deal with the tunneling out boundary condition
tiny revision base on last commit
change the architecture of boundary condition

- NEW : add the consideration of boundary direction, which is different from boundary condition direction in some cases
- ENH : add comment to the method for getting supply function in TrapToGateTunnelSolver, which has to be specially treated
- NEW : add the related methods in FDDomain
some revision based on new consideration of the boundary and boundary condition

- CHG : use boundary direction to determine whether an adjacent vertex exists, instead of using notTrapping method
- ENH : change the sign of the tunneling result according to known direction of the current density
- NEW : begin to deal with current density in the vertex physics
add the method to obtain electric field and current density

- ENH : enhance the consideration of class PhysProperty
- NEW : add the method to calculate electric field and current density
calculate and write electric field and electron current density

- ENH : some revision based on new consideration of the boundary condition
- NEW : use a new physics property to store the tunneling coefficient
- NEW : add the method for calculating electric field and electron current density
- NEW : add the method for writing electric field and electron current density
This version can output tunneling current. TunnelTag is introduced to boundary condition.

- NEW : use TunnelTag to distinguish tunneling-in and tunneling-out at the boundary
- FIX : fix a bug in calculating current density
- NEW : use TunnelTag to help to output the correct boundary current density
fix a critical bug in the normalization. previously abnormal current density is obtained

- FIX : fix a bug in normalization of tunneling out coefficient (in terms of density)
- ENH : some revision based on new consideration of boundary direction
-  NEW : add some methods in SctmData for debugging, i.e. writing total electron density in the trapping layer and the tunneling in current density and the tunneling out coefficient
enhance the dd solver structure

 - ENH : enhance the dd solver structure, for correctly dealing with the input boundary condition
tunneling-in and tunneling-out current is now seemingly currect

- FIX : fix a bug in reading tunneling-out current density at boundary
- FIX : fix a bug in calculating deltaX and deltaY
tiny revision based on last version

- CHG : change the name of some methods
Merge branch 'AddBndDirecDebugSolverPack'