Remove SVN ease-of-use functions from .bashrc.

In a situation where I would be able to use these, I would be able to
install Git, and I'm sufficiently at ease with Git-SVN that I prefer that.
Disable Vim Backspace binding.

I don't remember ever using this.
Fix comment.
Only map invhlsearch if terminal has colours.
Do not set max textwidth.

Firstly, 300 characters is far too long to be useful. Secondly, this is
a filetype plugin matter. Thirdly, it causes filetype plugin conflicts,
notably with Git commit messages.
Make Vim indentation 2 spaces.
Add bindings for Git rebase actions.
Remove spell checking bindings.

I always use aspell anyway.
Do not jump to last position in Git commit message.
Use Vundle package manager.
Add Vim Unite.