make password dialog really modal in external editor

solution: hide modal editor dialog when pwd dialog shown

bootstrap behaves a little strange when two modal dialogs are open at the
same time. This should be refactored, later, but for now it looks as
intended. At least with all the nested iframes, it’s hard to get it right.
We should switch to a more template based approach, in the future.
remove encrypt dialog when password dialog is cancelled

assume that user want’s to start all over, when cancel is clicked.
Don‘t close the whole editor, since there might be unsaved text in it.
make EncryptFrame::removeDialog method more robust

only remove dialog if it is there. This method might be called in inline
edit mode, when there is now dialog available. In this case, only the
password dialog needs to be closed.

This prevents a crash when hitting 'cancel' in password dialog when
inline edit mode is active.
indicate loading state for signDialog ok button

when the password dialog is shown, the ok button should be disabled to
indicate the process that is going on. The ui waits for the key to get
unlocked.
add a test page with some keys and PGP blobs

this makes testing the work-flow more easy. For now you can serve this
by running `python -m SimpleHTTPServer` in the `spec/` directory. A
serve task to grunt might be added, later.