* Add AMM bid/create/deposit/swap/withdraw/vote invariants:
- Deposit, Withdrawal invariants: `sqrt(asset1Balance * asset2Balance) >= LPTokens`.
- Bid: `sqrt(asset1Balance * asset2Balance) > LPTokens` and the pool balances don't change.
- Create: `sqrt(asset1Balance * assetBalance2) == LPTokens`.
- Swap: `asset1BalanceAfter * asset2BalanceAfter >= asset1BalanceBefore * asset2BalanceBefore`
and `LPTokens` don't change.
- Vote: `LPTokens` and pool balances don't change.
- All AMM and swap transactions: amounts and tokens are greater than zero, except on withdrawal if all tokens
are withdrawn.
* Add AMM deposit and withdraw rounding to ensure AMM invariant:
- On deposit, tokens out are rounded downward and deposit amount is rounded upward.
- On withdrawal, tokens in are rounded upward and withdrawal amount is rounded downward.
* Add Order Book Offer invariant to verify consumed amounts. Consumed amounts are less than the offer.
* Fix Bid validation. `AuthAccount` can't have duplicate accounts or the submitter account.
Adds two CMake functions:
* add_module(library subdirectory): Declares an OBJECT "library" (a CMake abstraction for a collection of object files) with sources from the given subdirectory of the given library, representing a module. Isolates the module's headers by creating a subdirectory in the build directory, e.g. .build/tmp123, that contains just a symlink, e.g. .build/tmp123/basics, to the module's header directory, e.g. include/xrpl/basics, in the source directory, and putting .build/tmp123 (but not include/xrpl) on the include path of the module sources. This prevents the module sources from including headers not explicitly linked to the module in CMake with target_link_libraries.
* target_link_modules(library scope modules...): Links the library target to each of the module targets, and removes their sources from its source list (so they are not compiled and linked twice).
Uses these functions to separate and explicitly link modules in libxrpl:
Level 01: beast
Level 02: basics
Level 03: json, crypto
Level 04: protocol
Level 05: resource, server
