convert license headers to SPDX

Includes license review of 3rd-party files, adding missing upstream
headers, and moving the UNSW OZPLB license into its own file rather
than replicating it in the header.

style-cmake.sh: fix line-wrapping in diagnostic

A backslash got wrapped to the next line, defeating the attempt at an
escaped line break.

style-cmake.sh: check version of cmake-format

Our settings work correctly only with cmake-format 0.4.x. 0.5.x causes
undesirable output.

Make style cleanups.

* misc/style-c.sh: Use the shell's && instead of "test -a", which is now
"obsolescent" per POSIX 2018 (see
http://pubs.opengroup.org/onlinepubs/9699919799.2018edition/).

* misc/style-all.sh: Indent branches of if-then-else conditional.

* misc/style-c.sh:
* misc/style-py.sh: [English] Prefer "in place" to "in-place" when not a
attributive modifier.

* misc/style-changed.sh:
* misc/style.sh: [English] Give comment sentences terminal punctuation.

* misc/cobbler:
* misc/style-c.sh:
* misc/style-cmake.sh:
* misc/style-py.sh:
* misc/style.sh: Standardize whitespace around CSIRO header.

misc: increase functionality of style.sh

- split style.sh into style-c.sh and style-cmake.sh
- add style.py, which passes files based on extension to the correct
style tools and ignores files specified in a .stylefilter file (only at
the top level)
- style.sh now calls style.py and expects a list of files
- add style-changed.sh, which styles all changed files in a git repo.
- add style-all.sh, which styles all files in directories passed to it