Fixed strict standards warning.

Made quickmail::delete_dialog() a static method.
Merge pull request #112 from ccle/delete_dialog_static

Fixed strict standards warning on delete_dialog
fixes static call to non-static method
Merge branch 'master' of github.com:lsuits/quickmail
Show side blocks, when composing an email
Merge pull request #115 from nadavkav/patch-1

Show side blocks, when composing an email
Disable multiple instances of this block

A teacher added (by mistake) two instances of this block to the course and we got a backup error.

I think this block should have only one instance per course. Am I right ?
Merge pull request #117 from nadavkav/patch-2

Disable multiple instances of this block

THANKS!