Update migration base.

[nedSaf]

@AronNovak @amitaibu @bitamar This is an update to the custom migration module.

I know this migration only has one handler for nodes and one for users but this is being copied into new projects and I would like to have all the common code and settings in the base and not in the handlers themselves.

The advantage is that unfamiliar developers won't have to copy this whole code to each new handler and familiar ones won't have to create their own new base.

Please review, whoever has a little bit of time, thanks :)

Note: I would like to add much more comments in the base to explain what each thing does but I'm not sure if it's just necessary.

[nedSaf]

No errors:

[AronNovak]

@nedSaf I like it generally, I added a few minor comments.

[nedSaf]

Thanks @AronNovak, I'll do the fixes.

[nedSaf]

Migration:

Content:

[nedSaf]

Update

• Fixed the comments.
• Upgraded the migrate module's version.
• Added some more docs for vars and logic in the base migration class.

[nedSaf]

@AronNovak Ready for a second review :)

[AronNovak]

:tada: