PDF rasterization now happens on demand.
NOTE: 2 fields added in base_source, so for exisiting DB, at least the following changes are required:
ALTER TABLE base_source add column x0 integer default 0;
ALTER TABLE base_source add column y0 integer default 0;
proof of concept of loading a PDF on-demand, when client only passes the PDF url.
- cleanup for old references to /admin
- each ensemble has a allow_ondemand parameter:
  Note that this change requires the following model change:
    ALTER table base_ensemble ADD column allow_ondemand boolean default false;
    update base_ensemble set allow_ondemand = false;
- add title for on-demand pdf (last part of the URL).
add script to generate pdf metadata
Merge branch 'master' into ondemand_pdf