1) Fix creation of new toplevel folders (and all its subfolder): it used to...

1) Fix creation of new toplevel folders (and all its subfolder): it used to generate a broken remote id and separtor ("i") causing weird problems.
2) Make sure toplevel imap folders are shown immediately, without a need to sync the account (workarounds an ETM bug 291143)
3) Warn the user if creating a folder failed on server-side and remove the folder locally. Otherwise if creation failed, it was impossible to create again a folder with the same name,
as it was already a folder with that name in the akonadi cache...
4) Make sure deleting folder "foo" doesn't deleted all folders starting with "foo" as it did before.
5) Just fix folder deletion. :) It could fail in certain cases.
6) Fix and adapt the tests.

Reporters of closed bugs: if you can still see the bug in 4.10.2, please reopen and state the details.

REVIEW: 109276
FIXED-IN: 4.10.2291143291143
BUG: 312435, 305269, 301088, 292418, 305987, 291143