relax SVN archive

The makefile has had two rules added, 'binary_dist' and 'source_dist'. The 'binary_dist' rule will
create the distribution archive files by first building the C modules, compiling the manual,
removing the temporary *.pyc, *.bak, and *.o files, archiving the files of the base directory
(excluding .svn directories) into the file relax-x.x.x.os.mach.tar.bz2 where x.x.x is the release
number taken from 'version.py', os is the name of the operating system, and mach is the machine the
C code was compiled on. Finally the file will be GPG signed (requires the relax private key!). The
'source_dist' rule will do the same but without the C compilation and all *.so files will be removed
as well.

The file 'docs/release_checklist' has been added. The file describes all the steps required for
releasing new relax versions.

The makefile 'docs/latex/Makefile' has been improved and a rule added for creating the manual
without executing relax.

The TODO file has been updated. Relaxation curve fitting has been removed as the code is complete.
It now has its own section describing the missing features of the technique.

The Swig file 'maths_fns/swig_jw_mf.i' and corresponding C file 'maths_fns/swig_jw_mf.c' have been
removed as they are not used and Swig was abandoned a while ago.