Make it easier to create branches

[hamishcampbell]

Is your feature request related to a problem? Please describe.

The only place you can create a branch is from within the Repo Log window by right clicking a particular commit to branch from. This is a bit obscure and I would expect to be able to create a branch from the right click menu of the Repo itself, and possibly from within the "Switch Branch" dialog.

Usually you want to create a branch from the current state of the Repository, so going into the Log shouldn't really be necessary for most use cases.

Describe the solution you'd like

Add a "create branch" option to the right click context menu for a Repository (or similar option).