Propose token whitelisting

There is a possibility of protocol DDoS.

daoConfig.maxPendingTokensForWhitelisting() was set by default to 5. In other words, more than 5 proposals could not be added for voting. The problem was that any user could add their own proposal, which opened up the possibility of a DoS attack. A hacker could either constantly ‘stuff’ the proposals to the maximum and block the addition of new ones, or frontrun unwanted tokens and also lock the system.