ToQUBO Compiler Upgrade

[pedromxavier]

This PR aims to make the reformulation modular, helping the development and testing of its current and subsequent features.

The necessary tasks to merge it are:

• [x] Fix the quadratization issues (closes #69)
• [x] Establish the Compiler module (closes #75)
• [x] Consolidate the Attribute System (closes #78, closes #79)

[codecov[bot]]

Codecov Report

Attention: 144 lines in your changes are missing coverage. Please review.

Comparison is base (ac8be79) 70.56% compared to head (96b02fd) 80.92%. Report is 2 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #77 +/- ## =========================================== + Coverage 70.56% 80.92% +10.35% =========================================== Files 24 31 +7 Lines 1247 1143 -104 =========================================== + Hits 880 925 +45 + Misses 367 218 -149 ``` | [Files](https://app.codecov.io/gh/psrenergy/ToQUBO.jl/pull/77?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=psrenergy) | Coverage Δ | | |---|---|---| | [src/ToQUBO.jl](https://app.codecov.io/gh/psrenergy/ToQUBO.jl/pull/77?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=psrenergy#diff-c3JjL1RvUVVCTy5qbA==) | `100.00% <ø> (ø)` | | | [src/compiler/compiler.jl](https://app.codecov.io/gh/psrenergy/ToQUBO.jl/pull/77?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=psrenergy#diff-c3JjL2NvbXBpbGVyL2NvbXBpbGVyLmps) | `100.00% <100.00%> (+17.02%)` | :arrow_up: | | [src/compiler/objective.jl](https://app.codecov.io/gh/psrenergy/ToQUBO.jl/pull/77?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=psrenergy#diff-c3JjL2NvbXBpbGVyL29iamVjdGl2ZS5qbA==) | `100.00% <100.00%> (ø)` | | | [src/encoding/encoding.jl](https://app.codecov.io/gh/psrenergy/ToQUBO.jl/pull/77?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=psrenergy#diff-c3JjL2VuY29kaW5nL2VuY29kaW5nLmps) | `100.00% <100.00%> (ø)` | | | [src/encoding/variables/interval/bounded.jl](https://app.codecov.io/gh/psrenergy/ToQUBO.jl/pull/77?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=psrenergy#diff-c3JjL2VuY29kaW5nL3ZhcmlhYmxlcy9pbnRlcnZhbC9ib3VuZGVkLmps) | `100.00% <100.00%> (ø)` | | | [src/model/qubo.jl](https://app.codecov.io/gh/psrenergy/ToQUBO.jl/pull/77?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=psrenergy#diff-c3JjL21vZGVsL3F1Ym8uamw=) | `76.27% <100.00%> (+1.69%)` | :arrow_up: | | [src/virtual/model.jl](https://app.codecov.io/gh/psrenergy/ToQUBO.jl/pull/77?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=psrenergy#diff-c3JjL3ZpcnR1YWwvbW9kZWwuamw=) | `100.00% <100.00%> (ø)` | | | [src/virtual/variable.jl](https://app.codecov.io/gh/psrenergy/ToQUBO.jl/pull/77?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=psrenergy#diff-c3JjL3ZpcnR1YWwvdmFyaWFibGUuamw=) | `100.00% <100.00%> (ø)` | | | [src/virtual/virtual.jl](https://app.codecov.io/gh/psrenergy/ToQUBO.jl/pull/77?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=psrenergy#diff-c3JjL3ZpcnR1YWwvdmlydHVhbC5qbA==) | `100.00% <100.00%> (ø)` | | | [src/compiler/build.jl](https://app.codecov.io/gh/psrenergy/ToQUBO.jl/pull/77?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=psrenergy#diff-c3JjL2NvbXBpbGVyL2J1aWxkLmps) | `90.62% <96.42%> (+9.26%)` | :arrow_up: | | ... and [20 more](https://app.codecov.io/gh/psrenergy/ToQUBO.jl/pull/77?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=psrenergy) | |

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