config/repo.list: url and rsync args update:

1. bioconductor is at 2.13 release now
2. pass --delete to rsync commandline to save disk space
roverlay/rpackage/descriptionreader.py: object() does not take an argument

The parent of DescriptionReader is object, which is created with object.__new__(cls).
roverlay-9999.ebuild: rovelay is no longer compatible with python2.7

Traceback (most recent call last):
  File "/usr/lib/python-exec/python2.7/roverlay", line 7, in <module>
    roverlay.defaultscript.main_installed()
  File "/usr/lib64/python2.7/site-packages/roverlay/defaultscript.py", line 35, in main_installed
    return main ( True, *args, **kw )
  File "/usr/lib64/python2.7/site-packages/roverlay/defaultscript.py", line 73, in main
    retcode = run_overlay_create ( main_env )
  File "/usr/lib64/python2.7/site-packages/roverlay/defaultscript.py", line 201, in run_overlay_create
    run_sync ( env )
  File "/usr/lib64/python2.7/site-packages/roverlay/defaultscript.py", line 177, in run_sync
    repo_list.load()
  File "/usr/lib64/python2.7/site-packages/roverlay/remote/repolist.py", line 128, in load
    self.load_file ( f )
  File "/usr/lib64/python2.7/site-packages/roverlay/remote/repolist.py", line 119, in load_file
    self.repos.extend ( new_repos )
  File "/usr/lib64/python2.7/site-packages/roverlay/remote/repoloader.py", line 82, in read_repofile
    **common_kwargs
  File "/usr/lib64/python2.7/site-packages/roverlay/remote/rsync.py", line 85, in __init__
    src_uri=src_uri, remote_uri=rsync_uri
  File "/usr/lib64/python2.7/site-packages/roverlay/remote/basicrepo.py", line 75, in __init__
    self._identifier = next ( self.__class__.ID_GENERATOR )
TypeError: IDGenerator object is not an iterator
bin/roverlay, bin/invoke_pyscript: fix $PYTHON

Don't execute scripts directly if $PYTHON is set.
roverlay/core: also log python version on startup
roverlay/util/counter: be compatible with python 2

Fixes d95efe157ea2a9e02eac805ae41fd340ac5e117c
roverlay/remote/websync: cleanup

* create distdir with mkdir_p=True (similar to rsync repo)
* print total number of files that will be synced
* _dosync(): check want_retry before retval
* _fetch_package_list(): add timeout to urlopen
roverlay-setup, init: fix config file location

Write R-overlay.conf to user_conf_root (or conf_root), not work_root.
roverlay-setup, init: fix config file location (#2)

+ handle standalone versions of roverlay
config/hookrc: remove debug/test entries
roverlay/stats, timestats: add reset() method

Fixes a bug when using the remote console ("./bin/debug/console remote") where
the second query_packages command fails due to reset() missing for timestats
objects.
roverlay-setup, config import: minor improvement

fs_ops.unlink() always succeeds in --pretend mode (no-op), so "roverlay-setup
--pretend" gives misleading output when user_config_root==config_root.

=> do not reset user_conf_root in --pretend mode if it isn't a symlink.
doc/: some updates
roverlay-9999.ebuild: reenable python2_7

add python2_7 to PYTHON_COMPAT, local test run succeeded.