[Feature Request] Supports `bare` repository

[love-linger]

I've pushed a branch feat-bare-repository that tries to support the bare repository.

The following features are available in that branch:

• Open a bare repository and add it to manage list.
• Support scanning bare repository under default clone dir.

[goran-w]

Thank you for this effort! It's already being useful, despite needing more work - I'm currently using bare repos while working on migration of several repos from Plastic SCM into Git.

A few things to fix:

• Under Local Changes, the Commit button should be disabled (grayed-out).
• Any Checkout / Merge / Rebase / Squash / Revert commands in context menus need to be disabled.

[love-linger]

I've merged the feat-bare-repository into develop since this feature is basically completed