Add automatic generated fortran support for setting and returning contexts

Major cleanup of the code for setting and returning application (previously called user) contexts
- PetscCtx ctx is now t

Add automatic generated fortran support for setting and returning contexts

Major cleanup of the code for setting and returning application (previously called user) contexts
- PetscCtx ctx is now the standard for passing in contexts
- PetscCtxRt ctx is the standard for passing out contexts, including context destroy routines based on PetscCtxDestroyFn

Both of these are typedef to void*

Also removed most use of user and userctx for context arguments now consistently named ctx

Improved documentation on PetscCtx and PetscCtxRt and on how to use contexts (including getting them) from Fortran

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Replace -with-mpi-f90module-visibility with -with-mpi-f90module=mpi_f08

Add PETSC_INT_KIND and PETSC_MPIINT_KIND

Reported-by: M.Weiland@epcc.ed.ac.uk

Fortran: enforce lower case keywords and operators

also fixed occasional capitals in used modules with the help of @prj-

cleanup suggestions by @BarrySmith

also noticed a few stray functions not marked as external and put them
into modules

place all the include statements at the top

Repeated inclusion in multiple location, e.g. at the start of a
module or function is not needed. This becomes clear if all includes are
outside of the ac

place all the include statements at the top

Repeated inclusion in multiple location, e.g. at the start of a
module or function is not needed. This becomes clear if all includes are
outside of the actual Fortran code.
Added regex to check that with the help of @sbalay

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Run fprettify