spetialization of linearSystemPETSc to avoid code duplication

can control its behaviour on empty matrices

destructor of the block solver

bindings (a better solution would be welcome)

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- fixed MED node ordering
- polished 64 bit Cocoa Mac OS X FLTK version
- updated copyright

linearSystemPETSc : move implementation to linearSystemPETSc.hpp included only in linearSystemPETSc.cpp. I hope it does not break petsc when compiled for complex. If it does, check the first lines of linearSystemPETSc.cpp (and send me an email :p --jon)

complex numbers

structure (not sure what was wrong though)

used in linearSystemPETSc for now)

Add a space manager to manage different function  space
Add a explicit solver (alpha generalized Newmark with damping)
Add a dynamic benchmark
Update benchmarks (the bulk mass must be given in argument)

LinearShell (Todo)
Add 3 benchmarks for shells 

modified

Some modification plate --> shell