crm, tools: improve mailgate
crm, tools: improve mailgate

- add X-TinyCRM in the header to prevent modification of the subject

ovnicraft/openerp-server,splbio/openobject-server,xrg/openerp-server,vnc-biz/openerp-server,MarkusTeufelberger/openobject-server,gisce/openobject-server,splbio/openobject-server,vnc-biz/openerp-server,gisce/openobject-server,splbio/openobject-server,gisce/openobject-server,MarkusTeufelberger/openobject-server,xrg/openerp-server,MarkusTeufelberger/openobject-server,ovnicraft/openerp-server