Misc cleanups:
* (typo) `highflag` => `highflag1`
* (typo) `lowflag = x = 0` => `lowflag == x == 0`
* Add structure and table of contents
* Describe more notation in words (e.g. `i`)
* Make sure flags are 1-bit
* Clarify and polish presentation
Example notation cleanups:
* `G1` => `id_G1` (to avoid confusing with the group G1)
* `field_modulus` => `q` (avoid using two names for same thing)
* `BLSVerify` => `bls_verify` (respect notation for functions in main document)
* `sig` => `signature` (avoid abbreviations as in main document)
TODO:
* Potentially describe `FQ2`, `b2`, `is_on_curve`, `multiply` in words
* Make the naming changes around `bls_verify` in the main document
* Fix any bugs introduced by the cleanup
* Partial draft of BLS-12-381 specification
* Some updates
* Updated point serialization to standard
* Added BLSMultiVerify
* Added domain separation logic
* Added point to hash algorithm
* Represented field_modulus as decimal along with the cofactor
* Added what e(x,y) means.
* Pass domain into hash_to_G2
* Updated code to make it more easily runnable in py_ecc
* Add pending review warning
