ngrease 0.1.0 released

This is the first downloadable release of ngrease.

The metalanguage has a fairly usable featureset. Several (small but non-trivial) languages
already work, and their implementations look quite promising for the usability of the
metalanguage. The coding conventions and even implementations need some cleanup, though,
since the project has evolved so much during their development.

At this stage things are probably not so smooth for a new ngrease user: error messages may
not be friendly enough, some expression variations don't work as expected (and are avoided
in examples) and so on.

The "standard library" contains only features needed so far in the examples. For example,
plus is the only arithmetic function... In theory anyone can create new "base" expressions
in the Java language, but this hasn't been documented. The author will add new expressions
as requested, if they cannot be based on the existing expressions using the ngrease language.

Some expressions in the standard library will probably change a lot or be removed, to get
a "natural and minimalistic" "axiom set" to base "higher level" expressions on.