Use repos.display_rev for revision numbers that are displayed in templates

[trbs <trbs@…>]

When using version control systems that are based on hashes of changesets, like Mercurial or GIT the revision numbers are often shorted or alternatively formatted so that the user doesn't have to see the large hex.

Therefor I've added display_rev on several places in Bitten so that templates always display the formatted revision number.

For example in Mercurial the revision number now looks like:

 386:b9d1f6a7318b 

Instead of:

 b9d1f6a7318b3300150d951a478448a3d03fb9df

Please look at the code and commit in:  http://bitbucket.org/trbs/bitten/changeset/338389921ce0

The patch is also attached :)

[hodgestar]

Looks good.

[trbs <trbs@…>]

There is one addition for the timeline at:  http://bitbucket.org/trbs/bitten/changeset/0a0bce41190a