Add TSV export, based on /Elements/TSVExport (4.2.4 and higher) or our own copy
Squelch warnings for configs set in RT_SiteConfig.pm

Because RT_SiteConfig.pm is loaded _before_ the plugins', and because
Set() doesn't override values that have already been set, the "default"
values in Assets_Config.pm cause warnings if overridden:

    Change of config option 'AssetQueues' at
    /opt/rt4/local/plugins/RT-Extension-Assets/etc/Assets_Config.pm line
    67 has been ignored. It may be ok, but we want you to be aware. This
    option has been set earlier in /opt/rt4/etc/RT_SiteConfig.pm

Squelch these warnings by skipping the Set() if the user has overridden
the value already.
Pass the correct class to ColumnMap

As Assets are mostly made of CFs, this _mostly_ worked, but failed to
pick up the right properties for roles.
Include the id in the format
Add a format to modify TSV downloads
More concise user display in assets

This makes better use of horizontal space.
With the previous commit, "User Summary" now has enough space to not need this
Merge branch '1.1/csv'
Merge branch '1.1/config-defaults'
Merge branch '1.1/people-display'