Prevent fetching already fetch changesets from already initialized branches

by removing branches when the changeset of child branch
is alredy found in the repository
Merge pull request #675 from pmiossec/improve_init_when_renames

Prevent fetching already fetch changesets from already initialized branches
Always setting the 'IgnoreBranches' parameter to a new repository
Detect 'IgnoreBranches' setting value to set (for existing repository)

when the value of the setting is not set
and depending of the number of Tfs remotes initialized
if at least 2 tfs remotes, then we want to support branches
otherwise, ignoring them...