[#18] Added documentation on configuration via jinja + yaml
More docs
Fixed problems with progress reporting

- We need to set the "group_name" field to NOT NULL and make sure we insert an emoty
  array to indicate "root" group; otherwise, the UNIQUE constraint will always accept
  new records if one of the fields is NULL..
Workarounds to some serialization problems..
Now replacing non-serializable exceptions with placeholder objects
better docs
Super-cool tracebacks
Added a script to check out the cool tracebacks
build['exception_tb'] is now a TracebackInfo object, created by the "core"
New testing job, with more facilities
Some more tests
ooops...
Now marking build as failed if the return value cannot be serialized
Tests for builds returning non-serializable objects / raising non-serializable exceptions
Added support for filtering build log messages
Minor improvement
Run buttons for jobs with unmet dependencies are now marked grey (fixes #19)
Nicer display of builds list
More tests for builds