Added proxy object in testcases.xml

  This override config.xml proxy definition (use "no_proxy" to disable proxy if set in config.xml)
 Added returnmessage set on verifs even if break_on_errors is off
  Failed verifications messages length reduced
  The goal is to get last failed verif message in output for each case if no errormessage set for the case
 Added a new hash to store global outputmessage
  The goal is to get all messages in the right order (execution order) whatever the number of testcases.xml files
 Added $self->{'config'}->{'httplogfile'} = "http.log"
  Use a specific http log file. It overrides default http.log file.
  Use it in config.xml <httplogfile>httplogfile.log</httplogfile>
 Added $self->{'cookie'} variable
  The goal is to regroup all cookies in the same file for a run but not global (cookies.txt).