Documentation: Revised intro & rename eBPF => BPF
Documentation: Revised intro & rename eBPF => BPF

 * Slightly more generic intro into the BPF guide
 * Replaced all occurences of eBPF with BPF unless the difference
   between cBPF and eBPF is being explained. We should start being
   consistent all around.
 * Project and talk references

Signed-off-by: Thomas Graf <5f50a84c1fa3bcff146405017f36aec1a10a9e38@cilium.io>

eloycoto/cilium,eloycoto/cilium,mskarbek/cilium,eloycoto/cilium,scanf/cilium,eloycoto/cilium,scanf/cilium,mskarbek/cilium,scanf/cilium,cilium/cilium,michi-covalent/cilium,michi-covalent/cilium,tklauser/cilium,cilium/cilium,eloycoto/cilium,mskarbek/cilium,tgraf/cilium,scanf/cilium,cilium/cilium,michi-covalent/cilium,tklauser/cilium,mskarbek/cilium,tgraf/cilium,cilium/cilium,gumpt/cilium,gumpt/cilium,scanf/cilium,tgraf/cilium,michi-covalent/cilium,gumpt/cilium,scanf/cilium,cilium-team/cilium,tklauser/cilium,tklauser/cilium,tgraf/cilium,gumpt/cilium,gumpt/cilium,cilium-team/cilium,tgraf/cilium,mskarbek/cilium,scanf/cilium,gumpt/cilium,tgraf/cilium,eloycoto/cilium,eloycoto/cilium,gumpt/cilium,michi-covalent/cilium,mskarbek/cilium,tklauser/cilium,cilium/cilium