Load messages of newly created account

Fix for #367 
See also https://github.com/owncloud/mail/pull/333#issuecomment-56743291

I double-checked and in master it never loads the messages for any newly created account unless I click a folder.
Can you @DeepDiver1975 @PoPoutdoor @jancborchardt @Gomez thos issue ?


There was no request for /messages, so I figured the issue was in the javascript.
The second parameter of ``loadFoldersForAccount`` contains the id of the account for which messages should be loaded after the folder listing has been retreived.

What do you think ?