Add AJAX updating to exports page

[Ed McDonagh]

And remove the auto-reload.

Partly because it is the right thing to do, partly because if the page loads before the job has been registered the reload doesn't get triggered.

[Ed McDonagh]

Initial AJAX view of current export tasks. Refs #575

→ <<cset afc19c88c3bf>>

[Ed McDonagh]

Initial AJAX view of current export tasks. Adding the template. Refs #575

→ <<cset d38a0ea27371>>

[Ed McDonagh]

Initial AJAX view of export tasks in error state. Adding the template. Refs #575

→ <<cset f786fb1f8d98>>

[Ed McDonagh]

Tested error table. Works, though would never currently happen as status is never set. Removed old static code. Refs #575

→ <<cset e5ccbaab401c>>

[Ed McDonagh]

PyCharm code reformat Refs #575

→ <<cset 479e5d132841>>

[Ed McDonagh]

Added the completed exports, but the refresh resets selection of the delete checkbox making it impossible to delete anything. Refs #575

→ <<cset 3597433728a1>>

[Ed McDonagh]

Added the completed exports, but the refresh resets selection of the delete checkbox making it impossible to delete anything. Forgot to commit the template again. Refs #575

→ <<cset 24ccb6764408>>

[Ed McDonagh]

Complete exports are now only generated once, with newly completed exports populating a new table, which fixes the issue of not being able to delete exports. Refs #575

→ <<cset 9fa8bbaf37d8>>

[Ed McDonagh]

Added select all checkbox at the top. Refs #575

→ <<cset 99d585dd490f>>

[Ed McDonagh]

Adding ref #575 to changes.

→ <<cset ee4b50007e4b>>

[Ed McDonagh]

Minor modification of refresh time for recently completed exports. Refs #575

→ <<cset 63a98c5fbb4d>>

[Ed McDonagh]

Removed import as per Codacy. Removed unused queries, switched render_to_response to render. Refs #575

→ <<cset 0990779c6277>>

[Ed McDonagh]

Merged in issue575exportsajax (pull request #143)

Fixes #575

→ <<cset e698f2672768>>

[Ed McDonagh]

Adding try except to prevent 500 error if no exports in the system. Refs #575

→ <<cset a95aa76ca5b2>>