Add new things to .gitconfig

* New aliases: `mt`, `dt`, `bra`, `brm`, `uncommit`, `unstage`
* Vim instead of nano
* Ignore file rights changes
* Default push behavior = only current branch
* Merge and diff tool Meld
* Various settings comments
* Removed aliases: `lg`, `lastf`, `last`
Add XFCE4-Terminal config similar to Gnome Terminal
Don't set $TERM from .zshrc

There's potential problem with that when you use some
old terminal or new one but in compatibility mode.
So this variable should be set by terminal or terminal
emulator by itself.
Add custom aliases file