Figure out Enterprise Update Handling

[Lsquared13]

Currently an Enterprise user can update their Dapp anytime. This implies

1. Their existing master branch may be overwritten
2. A user can buy a single Dapp, generate source for all of them, and use the source themselves.

Part of how we deal with this depends on pricing strategy, but we probably want to do the following:

• Don't allow updates to the ABI
• Put enterprise dapps in a DELETED state instead of actually deleting the item
• Continue to count DELETED items towards limits
• Allow create to replace a DELETED dapp with the same ABI

This is assuming a low incremental cost of additional dapps. If each dapp has a high incremental cost we may need to allow a limited number of updates