This commits adds a new loader class SvnLoaderFromRemoteDump enabling
to load svn repositories in an incremental way. The loader is based
on the creation of dump files generated with the rsvndump tool. Using
dump files allow to greatly speedup the loading process compared
to a client/server based approach.

Related T1161

Prior to this commit, the uncompression step happened in the __init__
call. Now, this happens in the prepare method.

This allows to have 'partial' visit if something wrong happens during
uncompression step (against None at the moment).

This commit ensures that the end of line style for each file extracted
from a svn revision respects the one defined by the svn:eol-style
property if defined.

Indeed, it exists some corner cases where badly formatted content
data were saved into a subversion repository (for instance a file
with CRLF line endings but with the property svn:eol-style set
to native) that prevent the subversion loader to succeed.

Closes T570

Related T982

This avoids digging in code to understand how to trigger messages

Related T982

Related T570

Close T948

Starting their commit range at 0 instead of 1.

Close T947

Remove no longer needed inheritance scheme.

Example: Svn repository with first commit in errors.