Spec ecosystem incentive

[taiki1frsh]

This PR is for the revision of the previous frontend-incentive module specification after the research about the things on check_list in there.
This PR is merged into the PR #216 . After merged, that PR also is merged into design/spec branch manually.

The changed parts from the previous frontend-incentive specification are not a few actually.

About module name
I changed module name from frontend-incentive to ecosystem-incentive because the current style can be applied for many different use-cases by using the same logic.

About logic
The biggest modification is definitely hooks part.
As you know, in the previous design, we planed to use event data for catching the traded fee information to accumulate rewards for the subjects.
But, after the research about it, it turned out to be impossible to do so.
Instead, there're hooks mechanism for cosmos sdk for literally hooking to some target actions.
(research log: https://www.notion.so/cauchye/Frontend-incentive-Tech-research-9b0965c91cd542ecbb6ea123d557add3)
By using this mechanism and the way to get memo data in a specific message process in the how_get_memo branch, we can implement incentive features without generating two-way dependencies between x/nftmarket and x/ecosystem-incentive modules.

And, following these changes, I decided to accept register style to become subject.

refs:
#218
https://www.notion.so/cauchye/Frontend-incentive-Tech-research-9b0965c91cd542ecbb6ea123d557add3

Please review and confirm, @mkXultra .

[taiki1frsh]

SetHooks usage in app.go:

chain/app/app.go

Line 461 in a9f86eb

app.StakingKeeper = *stakingKeeper.SetHooks(

chain/app/app.go

Line 555 in a9f86eb

app.cdpKeeper = *cdpKeeper.SetHooks(cdptypes.NewMultiCdpHooks(app.incentiveKeeper.Hooks()))

The location to define SetHooks in x/cdp/keeper/keeper.go:

chain/x/cdp/keeper/keeper.go

Line 57 in a9f86eb

func (k *Keeper) SetHooks(hooks types.CdpHooks) *Keeper {

[mkXultra]

@taiki1frsy
I think the data structure is ambiguous.
Can I see a sample data structure?

[taiki1frsh]

@mkXultra
I added description in 02_state.md for more abundant document of the data structures in this module.
Plz refer.

[mkXultra]

It might be better to have a Keeper Method that punishes it if there is a malicious front end.
It can be made to run with ProposalOnly

[taiki1frsh]

TODO:

• Add hook method to trigger the delete data about nft_id - incentive_id -> 84c62c1
• Define the locations to call above method -> 6613127
• Define Memo data structure -> https://github.com/UnUniFi/chain/blob/49626fce9aaf9965ae57bc4bcb893134e3600d55/x/ecosystem-incentive/spec/02_state.md#data-structure-for-the-memo-field

[taiki1frsh]

Memo:
Currently we don't have liquidation, auction, etc logic in the code yet.
So when we implement those stuff, the hook insertion must be included in there.