Rename DAE to DAO

[s-ben]

This PR renames the Decred 'Decentralized Autonomous Entity (DAE)' to the Decred 'Decentralized Autonomous Organization (DAO)' ( Closes #957 ).

[jholdstock]

Two places where DAE is still being used.

The first is an interesting case because it appears in the constitution which has only been modified in the past after having been approved by stakeholders. I believe changing this without a proposal is acceptable as this kind of change is not substantial - it is akin to fixing a typo.

dcrdocs/docs/governance/decred-constitution.md

Line 36 in 079ee00

* The project aims to transition to a Decentralized Autonomous Entity which controls the disbursement of Treasury funds.

The second instance is in a hyperlink and also requires one of the md files to be renamed.

dcrdocs/docs/governance/politeia/overview.md

Line 43 in 079ee00

1. Payment claims will be handled manually by Decred Holdings Group (DHG) until such times as this process can be handled by the [Decred Decentralized Autonomous Entity (DAE)](#decentralized-autonomous-entity-dae).

[s-ben]

The first is an interesting case because it appears in the constitution which has only been modified in the past after having been approved by stakeholders. I believe changing this without a proposal is acceptable as this kind of change is not substantial - it is akin to fixing a typo.

We discussed putting this name change up for a vote on Politeia. It was decided that unless there was significant opposition to renaming, it would be a waste of time doing a Pi proposal. So far nobody on chat, reddit, or GitHub has voiced opposition. I think a non-controversial name change in the constitution is defensible (and reversible if someone really feels strongly about it). Fine with not changing it there as well. @jholdstock