Check if quantity field valid when focus lost

OPEN - task 24: Create a stock module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/24
Validate if quantity not negative

OPEN - task 24: Create a stock module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/24
Throw with better exception message

OPEN - task 24: Create a stock module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/24
Impl transfer()

OPEN - task 24: Create a stock module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/24
Declare & Impl saveAndUpdateModel(List stockKeepers)

OPEN - task 24: Create a stock module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/24
Validate if src and dest warehouses are same

OPEN - task 24: Create a stock module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/24
Impl saveTransfer(src, dest)

OPEN - task 24: Create a stock module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/24
Declare & Impl saveAndUpdateModel(src, dest)

OPEN - task 24: Create a stock module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/24
Declare saveTransfer(src, dest)

OPEN - task 24: Create a stock module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/24
Specify JoinColumn name

OPEN - task 24: Create a stock module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/24
Impl transfer() with save(src, dest)

OPEN - task 24: Create a stock module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/24
Remove some obsolete validation code

OPEN - task 24: Create a stock module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/24
Fix logic error
Change the order of Observer registration

Registering warehouseModel after model fails to load itemsCombo in
startup
Undo remove warehouse from toWarehouseCombo
Dispose after transfer() complete

OPEN - task 24: Create a stock module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/24
Set JoinTable name
Add "Transfer Stock" func

Merge branch 'iss24-stock-module' into develop