Add a toggle function for changing a token transferability after initialization.

[lkngtn]

Note: this has been closed to be tracked in the "wishlist for future upgrades".

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Is your feature request related to a problem? Please describe.
Organizations created using the democracy template may want to convert to non-transferrable reputation org, or an org with a transferrable token may want to temporarily make all tokens non-transferrable as part of a recovery or token migration process.

On the flipside, an organization that starts as a non-transferrable may reach a point where it is advantageous to unlock tokens and make them transferrable.

Describe the solution you'd like
Create a function to toggle between transferrable and non-transferrable status of a token in the token manager. This function should be protected by a role.

Describe alternatives you've considered
Airdrops. But this feels both more wasteful (in terms of transaction costs) and disruptive (in terms of UX).

Additional context
This has been requested by a few organizations who want to start out with a non-transferrable token because non-transferrable tokens are less likely to be considered to be securities since they cannot be transfered/traded/sold, but eventually when the distribution of these tokens are sufficiently decentralized it the organization could collectively vote to enable transferability.

[sohkai]

This is fairly trivial to implement in the contracts, but would require an on-chain upgrade (that would be scheduled for 0.9).

[sohkai]

Closing; we will evaluate this when we plan new contract upgrades.