build.xml: Add compile-source-gen target

Also whitespace (untabify), and remove module.ceylon.formatter.version
from build.properties.
Add class, abstract, alias scripts for source-gen

I can’t be bothered to type out 'ceylon run source_gen.ceylon.ast' every
time.
Fix BaseType backend test

One of the type arguments was completely missing. Another instance of
the infamous “how did that ever work?” phenomenon.
Fix BaseExpression backend conversion

When there are no type arguments, the typeArguments of a
BaseMemberOrTypeExpression are not null, but JInferredTypeArguments.
I accounted for that in the conversion function, but somehow not in the
compilation function.
Add QualifiedExpression (RedHat’s QualifiedMemberOrTypeExpression)

    ", ".join
    process.arguments.first
“Fix” tests for ceylon/ceylon.language#480

parseInteger(), parseFloat() no longer parse full Ceylon integers or
floats, so I disabled some tests :(
CeylonExpressionTransformer: fix {Union,Intersection}Type

missing '.rest'… *sigh*
RedHatTransformer: fix {Union,Intersection}Type

another mising '.rest'… *heavy sigh*