Until now, the build directory contained a 'software/' directory (that
hosted all the built software), a 'tex/' subdirectory for the final
building of the paper, and many other directories containing
intermediate/final data of the specific project. But this mixing of built
software and data is against our modularity and minimal complexity
principles: built software and built data are separate things and keeping
them separate will enable many optimizations.

With this commit, the build directory of the core Maneage branch will only
contain two sub-directories: 'software/' and 'analysis/'. The 'software/'
directory has the same contents as before and is not touched in this
commit. However, the 'analysis/' directory is new and everything created in
the './project make' phase of the project will be created inside of this
directory.

To facilitate easy access to these top-level built directories, two new
variables are defined at the top of 'initialize.mk': 'badir', which is
short for "built-analysis directory" and 'bsdir', which is short for
"built-software directory".

HOW TO IMPLEMENT THIS CHANGE IN YOUR PROJECT. It is easy: simply replace
all occurances of '$(BDIR)' in your project's subMakefiles (except the ones
below) to '$(badir)'. To confirm if everything is fine before building your
project from scratch after merging, you can run the following command to
see where 'BDIR' is used and confirm the only remaning cases.

  $ grep -r BDIR reproduce/analysis/*
  --> make/verify.mk: innobdir=$$(echo $$infile | sed -e's|$(BDIR)/||g'); \
  --> make/initialize.mk:badir=$(BDIR)/analysis
  --> make/initialize.mk:bsdir=$(BDIR)/software
  --> make/initialize.mk:	$$sys_rm -rf $(BDIR)
  --> make/top-prepare.mk:all: $(BDIR)/software/preparation-done.mk

'BDIR' should only be present in lines of the files above. If you see
'$(BDIR)' used anywhere else, simply change it to '$(badir)'. Ofcourse, if
your project assumes BDIR in other contexts, feel free to keep it, it will
not conflict. If anything un-expected happens, please post a comment on the
link below (you need to be registered on Savannah to post a comment):

https://savannah.nongnu.org/task/?15855

One consequence of this change is that the 'analysis/' subdirectory can be
optionally mounted on a separate partition. The need for this actually came
up for some new users of Maneage in a Docker image. Docker can fix
portability problems on systems that we haven't yet supported (even
Windows!), or had a chance to fix low-level issues on. However, Docker
doesn't have a GUI interface. So to see the built PDF or intermediate data,
it was necessary to copy the built data to the host system after every
change, which is annoying during working on a project. It would also need
two copies of the source: one in the host, one in the container. All these
frustrations can be fixed with this new feature.

To describe this scenario, README.md now has a new section titled "Only
software environment in the Docker image". It explains step-by-step how you
can make a Docker image to only host the built software environment. While
your project's source, software tarballs and 'BDIR/analysis' directories
are on your host operating system. It has been tested before this commit
and works very nicely.