Sync codebase with sonata-doctrine-orm-admin-bundle

Synced codebase with that of `sonata-doctrine-orm-admin-bundle`. Just saying: I've tested it a while, but my testing was primary "Clicking around in my own test application" [1], so feedback is always appreciated (/cc @excelwebzone and @memphys :wink: But it seems their problem #79 is already solved @excelwebzone earlier this day).
To sum it up:
- It is not broken :smile_cat: 
- It fixes (somehow) at least two bugs I noticed earlier [2]

Note, that the changes sometimes are only adding, or removing empty lines, or changing comments, or similar. Thats because it made it easier to compare the files.

[1] At least with embedded documents/admins it covers an exotic topic.
[2] A "CSRF"-issue with embedded many-references and something with an "undefined index"-issue I forgot to remember ...