VCS: Enable terminating a command

Change-Id: I2160a22e300aca9b38e28257375c8e0be2026d12
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
VCS: Replace AbstractCheckoutJob with Command

Command now provides the same functionality. Deduplicate code.

Change-Id: I789f021050471281870b6ef6a81a94e66fbdf0c7
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
Git: Show progress on clone

When stderr is not a terminal, --progress should be passed
to display progress

Task-number: QTCREATORBUG-6565
Change-Id: I59ba731cab55d0dd7de5e11cefe7dd254505ee11
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
VCS: Use better terms on checkout wizard for DVCS

Change-Id: I9064c71787dbfb1eee6f8f473df39dda23a1252a
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>