Improved message on config file read error

Previously, "Error: could not find config file ???" was
printed when a config file could not be opened. This also includes when
the file had the wrong read permissions. Thus, an incorrect error
description was given (since the file actually existed).

This commit corrects this behaviour. This is done by introducing the new
error message "Error: could not read config file ???". This message is
now presented when the config file exists, but can't be read. The
original message is only presented when the config file actually does
not exist.

Additional tests are committed that ensures correct behaviour.

This commit fixes issue #61.
Added limit parameter for logs
Allow separate working directories for different instances of same program
Remove 'stdout' from getLogger - this doesn't appear to be used, so I expect it's not part of the published API.
Add some documentation on the POutputDispatcher
Extract method for setting up the main log
Remove repeat of getLogger signature in ServerOptinos.getLogger, and just delegate to loggers.getLogger. Added a comment to clarify the purpose.
Re-saved with excess whitespace removed
stub addHandler on DummyLogger
Separated setup of boundIO logger from filename-indicated loggers.
Implemented <channel>_syslog config parameters for process config
Restored support for also logging to stdout.

--HG--
extra : source : 8b4f022c867ea214784b5aa5edb244ddb809ffe5
Fixed incorrect key usage when setting up logfiles parameters

--HG--
extra : source : 93dba8a25ba4157b1411d6afbe8fbd0f2b1c10e1
Resave with excess whitespace removed

--HG--
extra : source : 4eb7b1bd8d707cc2643fdd35f4e0f794c142fc72
Due to the way handle_boundIO monkey-patches the logger, it's necessary to similarly monkey patch the logger here.

--HG--
extra : source : 0d23297286a2685c008e87aacfc690d857a0b68d
Updated another use of getLogger to use the new constructors.

--HG--
extra : source : b622386559fba4a8ef90a4451e8d578cdcf2854c
Moved SyslogHandler registration to a similarly-named function in loggers.

--HG--
extra : source : 8877155f89b3622e3db291b228b379a6c4e12643
Fixed failing tests now that the ProcessConfig requires the parameters.

--HG--
extra : source : 32505953b7d706d202284fa41d1398a92e1f29b9
Merge branch 'issue_61_pending' of git://github.com/JensRantil/supervisor into JensRantil-issue_61_pending

Conflicts:
	supervisor/tests/test_options.py
Fix markup