The <tt> tag is deprecated, according to:
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/tt

The <code> tag is proposed as a replacement. It has the same intented
semantics: an inline block of code:
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/code

Closes #41.

This is not simply fixing up spelling and grammar, but a full (ish)
review of English language strings and translation structure. This lays
the groundwork for a more formal translation round at a later date.

Some of the phrasing will inevitably be coloured by en_GB preference,
but I don't feel any shame about that.

Adding Django related i18n template tags so the string can be extracted
and filled into the language related .po files.

permissions talk of statements instead of agreements, and one can edit them even when having an ldap record

Introduced permission systems for see_agreements and edit_agreements, and started refactoring permissions tests

Analogous to the "Personal history" table on the person page, make incomplete
progresses a link to the progress page also in the process page.

Signed-off-by: Jonathan Wiltshire <jmw@debian.org>