Update frontpage_login.rb

Vhost is now used if specified.
Added X-Vermeer-Content-Type header, which seems to be required for the RPC service otherwise server responds with:
method=
status=

    status=262147
    osstatus=0
    msg=No "CONTENT_TYPE" on CGI environment.
    osmsg=
Extend replicants via arbitrary Ruby code

MSP-11673

* Implements a #register_extensions method on Msf::Module
* Any registered Ruby modules will extend the cloned module returned by #replicant
Just use constants directly

MSP-11673
Land #4280, frontpage_login improvements
Land #4298, arbitrary Ruby extension for replicant

MSP-11673

* Adds Msf::Module#register_extensions
* Extensions are arbitrary Ruby modules
* Allows overriding of psuedo callbacks
Bump metasploit-credential version
Merge pull request #4299 from techpeace/bump-metasploit-credential

Bump metasploit-credential version