Update draft-psenak-ospf-segment-routing-extensions.xml

1. Added Jeff Tantsura to the list of authors
2. Prefix-SID subTLV:
- added V-bit and L-bit
- moved Reserved field next to Flags
3. Adj-SID and LAN Adj-SID subTLVs
- replaced nested Sub-TLVs with SID/Label/Index 
- added V-bit, L-bit and S-bit
- moved Reserved field next to Flags