Issue #94: user administration improvements (conservancy/kallithea)

[Thomas De Schampheleire]

New issue 94: user administration improvements
https://bitbucket.org/conservancy/kallithea/issue/94/user-administration-improvements

Thomas De Schampheleire:

- e-mail sent to the administrator when a new user signs up should clearly state that his action is required to activate the account
- a link to the activation page should be present
- the web interface would ideally contain an easy way to activate one or multiple accounts, ideally by clicking one button and not requiring to 'edit' each account individually. A 'activate all non-activated users' button could also help here.