Fix commiting with Author and Email set on Windows.

Task-number: QTCREATOR-2397

... for git, hg as it is not obvious from the SHA1 displayed.

Provide UI with manual refresh button in BaseCheckoutWizardPage.
Change ProcessCheckoutJob to be able to execute several steps.
Implement in git.

Do not clobber environment setting for SSH_ASKPASS.
Pass on QProcessEnvironment to CheckoutWizard.

- Use message boxes on timeouts.
- Add a configuration for a graphical SSH password prompt binary with
defaults
- Launch commands that require authentification with no terminal on UNIX
and environment variable SSH_ASKPASS set accordingly.
- First attempt at introduce a common function to synchronously run VCS
commands in base plugin with flags.
- Use standard execution log entries in all VCS plugins (outputwindow).

... based on the git clone wizard. Provide a wizard for browsing
gitorious hosts.

Task-number:  44831

Task-number: 244831