Remove old and irrelevant files

[Gnappuraz]

This PR removes what I think is either outdated or not relevant for the repo anymore. Especially for spec_v1.0.md it contains outdated informations that can be quite misleading, I will create a new and up to date version of it. As for /particl/create_tx.md I think is not relevant at all at this point and should simply be removed.

[castarco]

ACK 983f410

[cmihai]

Concept ACK, but signal_callback_system.md still seems relevant?

[kostyantyn]

ACK 983f410

[AM5800]

I join @cmihai: what is wrong with signal_callback_system.md?

[Gnappuraz]

That signal_callback_system.md is incomplete and incorrect in some parts. Also is more bitcoin internals than stuff relevant to us. I'd rather remove it cause on its own also is a bit silly honestly, and not so useful.

[AM5800]

ACK 983f410

[cornelius]

The esperanza spec is linked from the Unit-e README. This needs to be corrected then as well. Would be good to have this information in the docs. We have an open issue for that (dtr-org/docs.unit-e.io#22).

[Gnappuraz]

@cornelius I'd rather get rid of it now, update it asap and republish it. Atm is really outdated on some parts, people reading it would just be confused I guess. We can directly republish it in the docs then.

[cornelius]

@Gnappuraz I'm fine with removing the files now as long as we make sure we don't end up with broken links in the unit-e README.

[Gnappuraz]

@cornelius I created a PR on unit-e to get rid of the links.

[cornelius]

ACK 983f410