Fix three typos, "equiped".
Non-impact changes to Defn 2.2.

I don't really like brackets.  In general, either things should be
included without brackets when they are important enough, or they
should be excluded when they are not.
Add a full-stop to the Lefschetz formula.
Non-impact change.  Change punctuation for "id est".

Previous usage was "i.e., " when this is essentially the
only non-standard usage.  One can use two commas around it,
or just one before.  I've opted for the latter option and
made this change through the document.
Non-impact change.  In Defn 2.8, remove brackets around semilinear.
Non-impact change.  Include non-breaking "~" on p3.
Non-impact change.  Remove brackets around "and this paper" on p3.
Non-impact change.  Remove line-break and add hyphen on p3.
Non-impact changes on p4.

* Remove an "and" in the first paragraph.
* Replace two instances of "get" on the page by nicer verbs.
* Add commas after the cases rather than after the env.
* Enlarge brackets for one expression.
Non-impact change.  Layout of Defn 2.14.
Non-impact change.  Remove brackets around "horizontal" on p5.
Non-impact change.  Change "Doesn't" to "Does not".
On p5, change the outline of the algorithm to "enumerate".

Note that this currently displays as (i), (ii), etc, which
does not look great.  We probably want to change this later,
but in any case, the list should be "ordered".
Non-impact change. Remove some brackets from the last item on p5.
Merge in Jan's changes.

The only conflicts arose around "sigma" which has replaced "sigma_p".