Preparing Release of SOMns 0.4

[Stefan Marr]

Hi:

We are preparing the next release, version 0.4.

The goal of the release is to have relatively stable version of SOMns that can be used, for instance as a basis for student projects.

The current changelog is attached below.

If there is any issue that should be fixed before the release, please let me know.

Best regards
Stefan

## Concurrency-Agnostic Debugger

This release introduces concurrency-agnostic debugging based on Kómpos.
It is realized by using a debugger protocol that abstracts from concurrency
concepts and instead uses a uniform representation and meta data that instructs
Kómpos how to understand and visualize breakpoints, stepping operations, and
data visualization

- introduced a uniform trace format ([PR #155](https://github.com/smarr/SOMns/pull/155))
- added process view
- refactor handling of breakpoints and stepping in interpreter and Kómpos
- added advanced stepping operations and breakpoints for STM, fork/join, actors, CSP, threads and locks

### Other Enhancements

- Switch to unified Truffle+Graal repo [PR #149](https://github.com/smarr/SOMns/pull/149)

- Updated to Truffle 0.25 [PR #132](https://github.com/smarr/SOMns/pull/132)

- Use precise array type check [PR #128](https://github.com/smarr/SOMns/pull/128)

- Make Kómpos tests more robust, include more info in failures, and use ephemeral ports if necessary [PR #144](https://github.com/smarr/SOMns/pull/144)

- Fix various single stepping issues [PR #143](https://github.com/smarr/SOMns/pull/143)

- Fix `#perform:withArguments:` primitive [PR #130](https://github.com/smarr/SOMns/pull/130)

- Make sure that `./som` without arguments does something useful [PR #156](https://github.com/smarr/SOMns/issues/156)

--
Stefan Marr
Johannes Kepler Universität Linz
http://stefan-marr.de/research/