Various (mostly whitespace) source tidyups

These make the source more readable while also ensuring that they
are parsed similarly by other markdown renderers. In particular
these changes are copied from my 'smallpeice-2014' branch in which
I used pandoc to create a PDF from the docs.

Change-Id: I3e3936816d661b7d9bfee7a05cda0d8e0cbdab7d
Fix another errant reference to the 'sr' module

Change-Id: I16e92bbd9dbf00c7172eb9718b5f555db4f5e08b
Merge multiple definitions of items

While it turns out that HTML5 is ok with having multiple dd elements
in the dl, it's not very visually pleasing to have horizontal lines
between each of the parts (and doesn't really make sense). Instead
just have each defintion part flow from the others and use <br />
where neccesary to keep the line breaks (since this is much more
visible in the source than a couple of trailing spaces).

Change-Id: Ib5a213880beaee9c4fcec0fa86cccdfa33096148
Whitespace wrapping

Change-Id: I78853fc5276949a7d09796981b44aa36db362cbd
Make intra-page links relative

There is no need for these heading self-links to be absolute. Doing
so actually makes them harder to read and more likely to end up
being wrong. Also fix a case where a heading didn't link to itself.

Change-Id: I5f89aa57d4e0dd50637f483d2caf6b2c5249066c
Fix errant 'io' attribute reference.

We've not had an io attribute on the Robot class for a very long
time. Replace it with a mention of the 'ruggeduinos' attribute instead.

Change-Id: I2871aeba4c48db906bf6acc540193f5e466b1263