Increase bucket name length

[orkunkl]

Is your feature request related to a problem? Please describe.
When I was implementing weave-starter-kit I found out bucket names must be lower case letters and between 3-10. This is quite constraining.

Describe the solution you'd like
What is the design choice behind this? If there are no implications why not increase the bucket name size? If not possible, we should document it in the code.

[husio]

@ethanfrey I am searching for a technical reason why bucket name must be between 3 and 10 characters and I cannot find any. Is this an arbitrary number that can be changed or there is a technical reason I cannot see?

Name building is using a : separator to separate bucket prefix from the key value. This should allow prefix to be any length.