Add option to create polls without staking

[ErkanKanden]

Depending on the subject matter of the poll, the author of a poll might want to give equal voting rights to all voters instead of having the staking bias. I know that one could use a traditional poll system on other platforms for this, but I would like to stick to the transparency, immutability and decentralization provided by the æternity blockchain protocol still. It would be great to have a feature where in the beginning of a poll creation, one can select whether to use absolute vote numbers or voting based on AE stake.