Fix memstats in renumber_positions(). Fixes #10

Added some calls to register_allocation in the subroutine renumber_positions
in the file Fields_Manipulation.F90. This is to prevent incorrect memory
stats at the end of a calculation.
This is a minor bug fix for the build framework. The Make.dependencies is not in sync with the code and thus causes make makefiles
to fail.
Allowing users to specify which multimaterial mean to use in the bulk_viscosity algorithm.

This has been implemented more generally so that all multimaterial averaging routines are capable of it regardless of rank but
nothing other than bulk_viscosity actually exposes the functionality.

A (very) short test has been added.
Make fluidity build with petsc 3.5

PETSC_DEFAULT_DOUBLE_PRECISION changed to PETSC_DEFAULT_REAL
KSP/PCSetOperators no longer have a MatStructure flag
As before, previous versions (3.1-3.4) are supported through macro hacks in include/petsc_legacy.h

Fixes #17
Remove depracated extended source stuff from configure.
Revert "Remove depracated extended source stuff from configure."

This reverts commit 9a85c0d7638f524e1f31e7853bc54aa34c63d41f.
Merge Fluidity master into compressible.