remove unused (but reserved) fields in eosiosystem::voter_info from ABI; add clarifying comments to system_contract::buyram fee logic

- Remove namespace from the class declared in EOSIO_ABI macro.
  This prevents the generation of empty abi files when the class used in the macro is fully qualified.
- Detect `//@abi action` in class methods. This allows automatic abi generation on contracts not using the EOSIO_ABI macro.
- Remove deprecated index detection
- Add f64 (double) as a primitive type

Also fixed error in transaction::send definition and added helper script
for abi generation.

Removed friend eosiosystem::system_contract

Move get_supply and get_balance methods to make them public

system contract bugfix: regproducer should always modify parameters (removed check if key is different) #3783

Old version was more difficult to decipher and also did not work for 13
character names.

Confirmed that the old version and new version behave the same way with
randomly generated names that are no greater than 12 characters. (That
code is not in this commit.)