Implement an "upgrade stats" command as a new self action

[HarrisonD123]

It would be cool if an upgrade command could be included to upgrade certain aspects of the current character (i.e. stats, skills, etc). The simplest command to start on would be "upgrade stats", which would involve a simple flat upgrade to all stats. The biggest unknown for this issue would be how to attach conditions to this action, given that upgrade stats might require different conditions (level for example) depending on how many times you've upgraded them.