This allows detection of some incorrectly-typed email addresses before
tickets, users, and agents are created.

This also adjusts the logic internally to lookup the priority by the
priority_urgency field, which should be constrained to follow priority
precedence over the priority_id field.

If failing to import file content data, drop contents imported thus far

This patch adds an export+import method to the file command line module. The
file export is agnostic of the file storage backend. It writes the files
with the %file record data to standard-out or to the file given by the -f
option. The file is a considered a stream and can quietly be compressed and
can be read back in as a stream (no seeking is performed in the import
process).

This patch also makes a slight edit to mPDF to allow better detection of
substitions in characters, as the DejaVu fonts shipped do not support Thai
glyphs.

If there is a problem installing some of the items with the system, try not
to crash simply because the error is passed into another ::create()
function.

And allow for @context to add context to the bare string literal. For
instance,

    /* @trans, @context "noun" */ 'Open'

Would mark the string 'Open' translatable with context "noun".

Make table prefix consistent

Implement the logic to set status

Help topics and filters can override the default status