Hierarchical structure of grants

### User Story

As a grant owner and a volunteer scientist, I want to make GitCoin grants hierarchical for more funding for foundational projects.

### Why Is this Needed

It is well known that science issues can't be settled by public voting. For example, science funding could not be distributed by a referendum or even by a parliament well. I have a mathematical project that is alone probably is as an important startup as the entire blockchain idea, for example. And I receive very little (close to "no") funding.

Quadratic voting is not an exception, it cannot distribute science funds and other foundational projects well, just because most people don't know well enough what to vote for.

### Description

*Type*: Feature

A better solution used in the centralized word is well know: _hierarchies_.

For example, for science projects professors vote, not general public.

So, I strongly propose to organize GitCoin grants into a hierarchy. The hierarchy should be editable in some way (hard to say how exactly, please discuss).

A possible way to edit the categories hierarchy is to allow anyone to create a new category and then to determine "how much" (in percents or in scores) each project belongs to each category by quadratic voting.

So, my scientific grant would go to a category like `Science` / `Mathematics`. People would quadratic vote how much to allocate for Science, inside the Science category they would vote how much to allocate for Mathematics inside science, and finally they would vote how much to allocate for my project inside Mathematics.

This would provide much fairer distribution to me :-)

Should we allow only experts to vote? Probably no need. It is unlikely that many people will vote for or against an algebra project if they don't know mathematics. But in the future we may think of some restriction to disallow unqualified people to vote in subtle categories.

### Current Behavior
Foundational (e.g. science) projects are often underfunded.

### Expected Behavior
Important foundational projects funded well.

### Definition of Done
Editable hierarchical structure of grants, hierarchical distribution of funds.

### Data Requirements
The measure of success is the amount of funding [this grant](https://gitcoin.co/grants/179/algebraic-general-topology?tab=description) receives :-) :-)