Fix various bugs found when testing strict SQL modes

[jpwhite4]

This pul request contains fixes for four different issues found when testing strict SQL mode. Each one is a different commit (for ease of review). The full changes needed to support strict SQL modes is a bit more involved - these are just the trivial ones.

Fix storage aggregator.

The physical_usage column in the fact table is nullable, but the one in the
aggregates table is not. This updates the load SQL to coalesce the null to 0 if necessary.

Fix SQL update string for XDUser

You can't call SQL function in PDO parameters. This code changes it so the that call to the MySQL
NOW() function is done good and proper like.

Update default values for XDUser's fks

Null is not an allowed value for the not null foreign keys to the organization
and person tables. This change initializes them to a valid value (-1 == Unknown)

Fix filter in Report Generator

The filter string was filtering out valid values for the Report Generator
delivery mode. This results in the valid string "E-mail" being converted to
a null which then getes converted to "E-mail" on the sql load if the
sql_mode is set empty. _Sigh_