Fix current working directory.

Previously, an 'OSError' exception was being raised by every 'os.chdir(dest_dir)', because we were changing to a directory that didn't exist, since we hadn't changed to the uppermost directory.
Fix error in command 'git submodule update'.

The subcommand had been misspelled (with a trailing 's'). Also, a 'git submodule init' has been added, because 'git submodule update' has no effect is 'init' has not been done before.
Add 'FIXME' annotations.
Add support for creating the build directory.
Add directory 'env' to '.gitignore'.
Add script to remove backup files (ended in '~') from the working directory tree.
Add compilation scripts for use with 'git bisect'.
Add execution permission for all users to 'clean_backup_files.sh'.
Add shell script to run all the example programs.
Add README to 'scripts' directory.
Add script 'bump_version.py'.
Add script 'publish_doc.sh'.
Merge branch 'scripts' into devel