auto account activations

New user registrations will not require invite codes any more. Accounts will be auto activated as long as the rate is within set limits. Beyond that, new accounts will be put into an auto approval queue, which shall activate based on a set rate.
nicer loading screen
faster loopback volumes with preloaded files

common files are pre-loaded on loopback disks to make them faster to assign to new sessions.
pre-loading is done when disks are returned to the pool.
upgrade to julia v0.3.3 build
Merge pull request #144 from tanmaykm/tanmaykm

auto account activation, better startup experience, Julia v0.3.3