Revision documentation

Added clarifying revision documentation from R1 to R51 and some general comments from R86 to the current R97. The point is that I'm successively learning some complex options of svn and the facilities (and lack thereof) of googlecode. The following pretty complex svn command generates a diff overview:

# svn diff --diff-cmd /usr/bin/diff -x '--brief'

In "the best of worlds" the syntax would instead have been

# svn diff --brief

or

# svn diff -B