Split generation of the config to make it more independant

[Cybertinus]

The generation of the config should be more modular. This has as advantage that when 1 part fails, the other parts are generated without problems. For instance: when the generation of the eBGP filter fails, the static routes towards our members should be generated just fine.

Parts that could be made separate, as a quick idea:

• eBGP filter en session config
• Transit config
• OSPF en iBGP config
• static routes toward the members
• BGP sessions toward the members
• Misc stuff in the config generation