Remove insert_column workaround

LAVA-1601 - django-tables2 has migrated to OrderedDict
from the deprecated SortedDict. This means that filters
need to create columns in the __init__ in the order in
which the columns are to be displayed, rather than re-ordering
later.

To manipulate the base columns safely, all columns in such
tables need to be instance variables, not class attributes.

Change-Id: I9921228571733e0605c52d79740903adad3d0d3d
Implement delta reporting.

New db field for image charts, new field on UI and calculation
changes for delta reporting.

Implements https://cards.linaro.org/browse/LAVA-1508

Change-Id: I744ae225755f72dd50cacf4c30d993ace26db8c4
Enable django logging

Restore django log files as the equivalent of the old
wsgi log files with support for logging from the classes
as well as errors.

Add support for django_auth_ldap logging.
Adapt existing dashboard_app logging to use this support, set
at INFO level by default.
Add sample debug call to lava_scheduler_app.

Change-Id: If505f8738e3b4a29406bc2c37619a1f14afff1d0
pep8 fix

Change-Id: I47d2d1f4596fdd156bfb9bc5f55abf34aeac35a0
Clarify meaning of the LAVA hostname

Change-Id: I0482180030b8de42311bde45a479351f86071bf0
Revert "LAVA-1488: View JobTable without health checks."

Fix bug #761 - enabling discrete queries by default causes 
simple searches to be disabled.

This reverts commit 59018765341d383dec53c46d3d8e9d5db00d6a5a.

Change-Id: I51092213eb8d5585fc5ab9ddb4254dbf4ed1ad77
Catch early job failure

Change-Id: I7cd14c68ed6e9dc2e9844eeadbc6732417ad6196
Ensure log message is only on error

Change-Id: Ib006c1aac32f2e968c978dbbe2995a07b1a6df4d