initial commit to add multiple electrodes in PVMOS
incremental work
adapted mesh2d.h and mesh2d.c to allow for a variable number of electrodes
this should enable:
- 3D simulations of conduction in a thick electrode
- simulation of tandem devices with conductive contacts between the component cells
  including e.g. shunts oon only one component cell
- inperfections in electrode on electrode systems (e.g. metal grids with fingers
  which are disconnected from the base electrode)
TODO:
adapt solve.c to allow for multielectrode systems
adapt parse.c and parsedef.h to allow the parametrization of the system
Perhaps I should also implement a function to delete an electrode (to add one has
been implemented).
added variable number of electrodes, i.e. PVMOS is a full 3D solver now!
folowing has been implemented:
	- I can add electrodes in a mesh
	- Specify electrode properties and inter-electrode connections
	- all electrodes can be connected to the positive node or ground
I tested against previous version and 2 electrodes, valgrind, and
tested adaptive meshing. All seems to work well so far
This commit cleas the way to implement thermal models where I need a
3D Poisson solver, which just happens to be what I have now...
corrected some small errors in memory allocation and fixed the read/write mesh routines
fixed some small bugs in dataexport:
	- Some small bugs in the routine to compute current densities and electric fiels in electrodes
	  some of these bugs were old some were introduced when extending the code to an
	  arbitrary number of electrodes.
	- Fixed bug in SolveVa, where only the data for the last voltage was stored appropriately.
Many small bug fixes
+ headers in output files
+ fixed bug in mesh allocation when merging meshes
+ added mkpvmosmesh, an octave library for writing PVMOS meshes
added license text
added the examples
PVMOS version 0.5
- Updated documentation
- Updated README
- Fixed bug in refine_coarse where it would stop refining prematurely
- Added the remove meshvar command to delete obsolete meshes (saves memory)
- Added small thin film example (does not require GNU Octave to run)
- Changed selection routines to be able to select a sub-set of the selected nodes
- Added a function to select nodes per area (very useful in combination with the first point)

Seems that sometimes Nodeconnector failes to connect nodes. I increased the TINY value to resolve this issue but more testing is needed.
Several changes:
	- Improved maintainability of the parse routine by adding a
	  routine that fetches a number or arguments from the input
          file and stores em in an array of strings
	- Made output prettier by enforcing a linewidth of 64
	  characters and wrapping longer lines
	- Added routine to select elements clode to a polygon
	  contour. This is useful for cracks and for refining the
	  mesh such that a polygon fits in accurately.
Added the CSiSTD example files