Non-voteshare markets
Using the lmsr algorithm, all contracts are actually voteshare contracts. Several contracts are grouped and will always sum up to 100%.
A trick to bypass this and add probability contract is to use an invisible, mirror contract. So when the administrator adds a new probability contract on, say, "Likelihood that the sun will set" with a starting price of 99, an invisible mirror contract "Likelihood that the sun will not set" will be generated with a starting price of 1. The users will not see the second contract.
The data for the contracts needs to have a flag showing whether a contract is a probability contract, the UI needs to hide the mirror contracts and the administration interface needs a switch on the create market page. There should also be some sanity checks preventing the administrator from creating multi contract probability markets.