Ticket #2796: don't allow arbitrary overriding of the 'action' class and other parameters pulled from the URL mapper.
Ticket #2796: don't allow arbitrary overriding of the 'action' class and other parameters pulled from the URL mapper.

This protects against oddities such as manual invocation of the ClientError action, which can spoof error messages.

zcopley/zcopleys-statusnet-clone,chimo/social,bankonme/gnu-social,studio666/gnu-social,eXcomm/gnu-social,sikevux/bsk-social,d3vgru/StatusNet,charlycoste/StatusNet,xebia/statusnet-oauth2,zh/statusnet,studio666/gnu-social,UngPirat/freesocial,minmb/statusnet,faulteh/gnu-social,charlycoste/StatusNet,xebia/statusnet-oauth2,furtherfield/gnu-social,charnimda/lgbtpzn-social,faulteh/gnu-social,csarven/statusnet,studio666/gnu-social,sikevux/bsk-social,gnusocial/mainline,csarven/statusnet,faulteh/gnu-social,Piratas/tortuga,Piratas/tortuga,xebia/statusnet-oauth2,chimo/social,gnusocial/mainline,eXcomm/gnu-social,chimo/social,zcopley/StatusNet,eXcomm/gnu-social,Piratas/tortuga,minmb/statusnet,studio666/gnu-social,zcopley/zcopleys-statusnet-clone,furtherfield/gnu-social,shashi/StatusNet,gnusocial/mainline,furtherfield/gnu-social,d3vgru/StatusNet,zcopley/zcopleys-statusnet-clone,zcopley/StatusNet,foocorp/gnu-social,foocorp/gnu-social,bankonme/gnu-social,sikevux/bsk-social,shashi/StatusNet,sikevux/bsk-social,zcopley/StatusNet,charnimda/lgbtpzn-social,faulteh/gnu-social,foocorp/gnu-social,gnusocial/mainline,eXcomm/gnu-social,furtherfield/gnu-social,csarven/statusnet,Piratas/tortuga,d3vgru/StatusNet,zh/statusnet,UngPirat/freesocial,minmb/statusnet,bankonme/gnu-social,UngPirat/freesocial,shashi/StatusNet,bankonme/gnu-social,charlycoste/StatusNet,zh/statusnet,csarven/statusnet,charnimda/lgbtpzn-social