fix uncaught exceptions during fetch and find

We encountered several issues with graphite-web when running in a high
availability setup and when switching off a node.

This helps with the following excetpions (and maybe others):

```
  File "/opt/graphite/webapp/graphite/readers.py", line 30, in waitForResults
    return self.wait_callback()
  File "/opt/graphite/webapp/graphite/remote_storage.py", line 208, in extract_my_results
    for series in wait_for_results():
  File "/opt/graphite/webapp/graphite/remote_storage.py", line 203, in wait_for_results
    raise Exception("Passive remote fetch failed to find cached results")
Exception: Passive remote fetch failed to find cached results
```

```
  File "/opt/graphite/webapp/graphite/readers.py", line 30, in waitForResults
    return self.wait_callback()
  File "/opt/graphite/webapp/graphite/remote_storage.py", line 208, in extract_my_results
    for series in wait_for_results():
  File "/opt/graphite/webapp/graphite/remote_storage.py", line 182, in wait_for_results
    response = connection.getresponse()
NameError: free variable 'connection' referenced before assignment in enclosing scope
```

```
  File "/opt/graphite/webapp/graphite/readers.py", line 30, in waitForResults
    return self.wait_callback()
  File "/opt/graphite/webapp/graphite/remote_storage.py", line 208, in extract_my_results
    for series in wait_for_results():
  File "/opt/graphite/webapp/graphite/remote_storage.py", line 182, in wait_for_results
    response = connection.getresponse()
  File "/usr/lib64/python2.6/httplib.py", line 990, in getresponse
    response.begin()
  File "/usr/lib64/python2.6/httplib.py", line 391, in begin
    version, status, reason = self._read_status()
  File "/usr/lib64/python2.6/httplib.py", line 349, in _read_status
    line = self.fp.readline()
  File "/usr/lib64/python2.6/socket.py", line 433, in readline
    data = recv(1)
error: [Errno 104] Connection reset by peer
```

Also, this might be related to #421
don't copy irritating example conf files in post install, which will not belong to the rpm
make the number of bootstrap days for all holtWinters configurable
configure NullHandlers in case logging is not requested

We frequently see error messages of the form:

[Tue Nov 12 01:06:53 2013] [error] No handlers could be found for logger "cache"

This commit fixes that issue.
reconfigure the metricAccessHandler

Make it have a backup of 1 file, like all the other Rotators. Also, this logger
isn't even used anywhere, so it will not matter.
introduce a function to configure loggers
configure infoLogger via function
configure exceptionLogger via function
configure cacheLogger via function
configure renderingLogger metricAccessLogger via function
make log rotation configurabel
fix import
midnight should be a string
adding test file for logger
improve tests

Test various aspects of the logger module.
add docstrings to the unit-tests
update comment
check that deactivation of log file rotation works
adding tox testing for python2.6 and python 2.7
fixup NullHandler for python2.6