Allow user allocation of storage space

[rosefox]

Title
Allow user allocation of storage space

Short, concise description of the idea
Allow users to allocate their storage space.

Full description of the idea
Let users allocate LJ file storage space in ways that are appropriate to our use: X% to userpics, Y% to voice posts, Z% to uploaded media files.
An ordered list of benefits

• Less complaining from users like me who almost never make voice posts but would really like more userpics, or vice versa.
• Add-on purchases could be consolidated into the single option of purchasing more storage space.
• Maybe further down the line, users could also make gifts of storage space, either by buying it for another user (as with paid account status) or by donating it from their own stock.

An ordered list of problems/issues involved

• Might be technically tricky to implement.