Remove `httpd-beacon.conf' at make clean.

Updated Make target 'clean' to remove file `httpd-beacon.conf' for
it is generated by the `./configure' script.
Remove white spaces.

Changed BeaconAPI.php to remove unnecessary white spaces.
Write log messages to beacon.log.

Changed `error_log()' calls to append error messages to a file
`beacon.log'. Changed the message type from 1 to 3 so as to
append the log message to a file, rather than send it via email.

  see -> http://php.net/manual/en/function.error-log.php
Merge branch 'master' of github.com:satya/beacon