Harmonize README locations

[haerdib]

We currently have several README and Tutorial locations. There are local Repo READMEs (Integritee & encointer), the Integritee (& SCS) Wiki and the Book. Several duplications are there and not everything is kept up to date.

We should do the following:

• Decide which information should be documented where. Inform the Team about the decision.
• Remove redundant information, and maybe place the link to the information instead.
• Update outdated information

Example:

• Runtime upgrade policy information is in the README of encointer and Integritee parachain. But it's also good to know for the Integritee node. So where should this information be placed?
• Build information of the integritee node is in the local README (quite outdated) and in the integritee book (several locations as well: https://book.integritee.network/howto_node.html oudated, https://book.integritee.network/howto_private_tx.html up to date)

[haerdib]

Goal: Detailed Docu in the gitbook. The README in the repos should link to the gitbook and be very minimal (E.g. no double maintenance of READMEs)

[haerdib]

in all Repos & all readmes