web: fixes related to account-creation disabling

- Correctly enforce the following config options:
    <disable_account_creation>
    <disable_account_creation_rpc>
    <no_web_account_creation>
- On the project front page, if account creation is disabled, say so.
- on other pages, if account creation is disabled,
    don't show a "create account link"
Merge branch 'master' of ssh://boinc.berkeley.edu/boinc-v2
remote job submission: typo in create_batch() RPC