Reimplement connection between InstantTranslate and TermPortal

See attached screenshots

For this behavior it needs to be taken into account, if the current user has a TermPortal role (if he is in InstantTranslate) or the InstantTranslate role (if he is in TermPortal).

Only then the connection functionality is offered.

The same is true for the menu switch between InstantTranslate and TermPortal

translate5 remembers the last used functionality (TermPortal or InstantTranslate - the backend functionality for this behavior is already there) and reopens this one on next login. If the user did never log in so far, by default he will see InstantTranslate, if he only has the right to see InstantTranslate and TermPortal

When a term is added to TermPortal as proposal from an MT language resource in InstantTranslate, a comment (note attribute) "Added from MT" is added to the note field of the source and that of the target term. This is fine. Yet the note field of the target term should still be open for editing, so that the user can add more notes, if he wants and saves it manually.

 If a term is added from InstantTranslate to TermPortal (see screen) and there is more than one TermEntry with the source term from InstantTranslate, a notice should appear, that tells the user, "Please select one of the source terms in the left column. They belong to different term entries. After selection you are able to add your new term translation to translate5 termPortal." / "Bitte wählen Sie einen der Quellbegriffe in der linken Spalte aus. Sie gehören zu verschiedenen Begriffseinträgen. Nach der Auswahl können Sie Ihre neue Termübersetzung zum translate5 termPortal hinzufügen."

The option "InstantTranslate into" should only be available for languages, that are available as target languages in InstantTranslate. Not for all languages available in TermPortal. 

For more details, what is implemented in the old TermPortal and has to be reimplemented, see https://jira.translate5.net/browse/TRANSLATE-1371