Kernel Performance Improvements

[regular-citizen]

Here are collected changes to the CaTT kernel to improve checking speed for large terms. This is necessary for checking cones in higher dimensions.

[thibautbenjamin]

I rebased this branch on #58.

Here are a few things to fix:

• build process using landmarks optioinally
• oracles for the tests are wrong, with very weird feedback

[thibautbenjamin]

I moved the commit that removes the context from the types in #72 since it is more involved and requires carefully ensuring invariants to prevent unsoundness. The other commits from this branch however should be merged for the release

[regular-citizen]

Approved