Move calls to CRM_Core_BAO_FinancialTrxn::createDeferredTrxn back to the calling...

Move calls to CRM_Core_BAO_FinancialTrxn::createDeferredTrxn back to the calling functions.

Although this seems like we are increasing duplication - by having more calls to one line of code I feel like
we are better off moving it back to the calling functions as there is 'preparatory wrangling' that also belongs
in the calling functions - notably in changeFinancialType.

I believe we should be able to get to the point where the updateFinancialAccounts funcgtion does not
need to receive context as a parameter because all the context specific stuff will be done in the calling functions
and it will have a clear objective - which I have finally realised is creating the financial transaction
and the financial items - however in some cases it is called twice to do a reversal followed by a line item
and I believe the calling functions could be cleaned up a lot more by 'returning' code to them as
passing  by reference leaves us very unclear as to what is happening to them at each point in the process.