Update export to handle int64 cases.

Context

Fix #306 (closed)

Modified files

• imp: export now handle int64, int32, int16, int8 (and unsigned variants) inputs and outputs.

Detailed major modifications

IMPORTANT @axelfarr @olivierbichler

• Headers in forward jinja are no longer automatically prepend with "" in the jinja. This is now done in shceduler_export in order to enable system includes with <>. The new logic is that if the include doesn't have "" nor <> then we add "".
• forward.hpp now has all the include of forward.cpp. I am not sure if this will create issue oin the binary size, but this ensure the declaration of forward functions with int64 types are well defined. I was not too sure of the need of creating a separated listfor header and soruce... If there is one then I can create two different lists.