Add branch option for workflow tab

[canack]

User can switch the workflow's branch before the trigger.
Implement a textbox that have autocompletion feature. Use project's default branch as default.

[canack]

I think, we can make a feature like this:

Like trigger tab, we should accept inputs..

How to implement:

• Fetch all branches of repository
• Add text input and add all branch names into suggestion list into text input
• Activate suggestion feature
• When select a valid branch, change branch value of this shared variable:

	// shared properties
	SelectedRepository *hdltypes.SelectedRepository