refactored to use new Loglines dictionary to keep track of logical
token names per LogfileInput
added test and code to verify that the logger is overridden in the PipelinePack.Message object
added docs for the new Logfiles subsection and a sample configuration of LogfileInput
changed LogFiles back to a single filename and added a logger
attribute to LogfileInput to specify the logger per LogLine
Merge branch 'dev' into features/issue_137

Conflicts:
	docs/source/configuration.rst
	pipeline/inputs_test.go
	pipeline/logfile_input.go
got rid of the discover map and converted it to a simple bool as we no
longer have multiple files to monitor
got rid of seek map and converted it to simple int64
got rid of ident_map and switched to just a string logger_ident
got rid of filedescriptor map
fixed incorrect sample syntax for LogfileInput
Merge branch 'dev' into features/issue_137
renamed fds to fd
Merge pull request #222 from mozilla-services/features/issue_137

Features/issue 137