AbstractScriptEngine: add API to access the LogService

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
AbstractScriptEngine: use SciJava context's LogService

... if available...

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Beanshell: use LogService via just-added API

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Beanshell: organize imports

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Beanshell: return the actual entry set

We constructed the entry set of the bindings, but then returned null
(a left-over from times when we still had to implement the entrySet()
method).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Add a JavaDoc for Beanshell

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Add support for Jython

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Bundle Jython support with the application

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>