(cherry picked from commit a9823b6b)

This is the #1 cause of Fatal Errors in Mahara - when a second exception (usually an SQLException) is thrown while we're in the middle of handling one already.

Now the first exception gets to follow through to its conclusion, which results in far better error messages.

(cherry picked from commit 56d85a5a)

(cherry picked from commit b0b42ae0)

This will make it easier to debug such problems in the future.
(cherry picked from commit 8c869919)

Defense in depth - run some vars through |escape, although we know that currently they're safe vars.

Conflicts:

	htdocs/artefact/blog/theme/default/render/blogpost_renderfull.tpl

Force profileicon upgrade to fail if dataroot/artefact/file/profileicons directory exists; don't try to delete profileicon artefacts without files on disk

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