Modify default value for a few cgitrc options

The default max-length used when printing commit messages and repo
descriptions can be increased due to the new layout (no sidebar).

Also, on the repo summary page I believe it makes sense to only show the
ten most recent branches and tags by default, just as it makes sense to
show the ten most recent commit messages for the active branch.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>