add a test of transfer matrix

impliment transfer matrix method for small size to bench mark DMRG.
open a new branch for multi-mode DMRG
Use HUGE_TENSOR and DATAPOOL

1. add module MATH with HUGE_TENSOR type defined. also provide RESCALE
subroutine to scale the tensor. remove free energy FA, FB feasure,
upgrade DMRG to deal with HUGE_TENSOR directly.

2. add module DATAPOOL to hold DMRG data, along with subroutines to
allocate and associate data pointer with the data block. DMRG kernel is
updated to exchange data by DATAPOOL directly. however, the measurement
functions has not been updated to access DATAPOOL yet for this commit.

3. upgrade TENSORIAL. add ZVAL to get value of a scalar tensor. upgrade
NORM -> SCALE to get overall scale of a tensor.

4. update gitignore.
try made multi-mode solver failed
Revert "Use HUGE_TENSOR and DATAPOOL"

This reverts commit 1e75352e5859c5ddf9039fe66a3bcb039b48b1c6.

Conflicts:
	DMRG
	DMRG.f90
	build/DMRG.o
	build/physics.mod
	build/task.mod
	build/tensorial.mod
Revert "try made multi-mode solver failed"

This reverts commit 1e75352e5859c5ddf9039fe66a3bcb039b48b1c6.

Conflicts:
	DMRG
	DMRG.f90
	build/DMRG.o
	build/physics.mod
	build/task.mod
	build/tensorial.mod
Revert 1e75352..5731c58

This rolls back to commit 1e75352e5859c5ddf9039fe66a3bcb039b48b1c6.
Revert 47a260a..bb2f4ec

This rolls back to commit 47a260a6c6c82f75f605d834259975780a17dc96.
Failed Attempt to write multi-mode solver by Arnoldi iteration
Add diagonal subroutine
Revert 1e75352..44b6a84

This rolls back to commit 1e75352e5859c5ddf9039fe66a3bcb039b48b1c6.
Merge pull request #8 from EverettYou/fDMRG

F dmrg