Move ccsljava documentation to the execution-moccml repository

[dvojtise]

the documentation about using ccsljava (aka. moccml) is currently in https://github.com/eclipse/gemoc-studio/tree/master/docs/org.eclipse.gemoc.studio.externaltools.doc/src/main/asciidoc/ccsljavaxdsml

Ie. external because the engine wasn' integrated in the studio when the project moved to eclipse organization.

As the moccml is now part of the studio again (https://github.com/eclipse/gemoc-studio/issues/146). The documentation should be moved to a better place. Probably directly in https://github.com/eclipse/gemoc-studio-execution-moccml/

(obviously it should also be verified, but this is another issue :wink: )