Fixes #74. Logger messaging works in the proxy module

A logger method was introduced as well as a mechanism for logging if this
code is run as a standalone cgi service

fixes #74 - tftp and puppet ca errors are not shown in the log file

added some basic error handling

Changed default TFTP dir to be a subdir of GNI.

force file rewrite, avoids FileUtils exceptions

built function and puppetca proxy now works

added some basic validations if the file exists

added a build action, this triggers all required actions (e.g. PuppetCA, DNS Tftp etc

created a proxy plugin, this plugin access the different gateways (e.g. dhcp/dns/puppetca/tftp etc)