cylc gpanel: add traceback handling
Attempt to move all database access to main thread.
Single rundb thread working for restarts and reloads.

 * also fixes out of order message setting of db status.
Remove redundant db calls.
gcylc: add uncaught exception dialog
Merge branch 'gpanel.fix-idle-start' into gcylc.gui-exception-dialog
gcylc: add cylc gpanel error report
Added a new submit-retry task state.

Functionally equivalent to execution retry, but useful nonetheless.
Merge branch 'master' into submit-retry-task-state
Merge pull request #613 from arjclark/db-single-access-hack

cylc: single db access object
gcylc: modify error report text
Merge pull request #618 from benfitzpatrick/gcylc.gui-exception-dialog

Exception handling for cylc GUIs
Merge pull request #619 from hjoliver/submit-retry-task-state

Added a new submit-retry task state.