evolve: extract displayer to _solveone()
I extracted this displayer method to _solveone() so that it would be
easy to pass a different template to show evolve msgs. In upcoming
patches we will be using stacktemplate in some cases where we want
to include stack alias s# in evolve msgs.
Doc is generated with sphinx.
You can generate the doc with:
```
make
```
# Tutorials
For updating the tutorials, you need to have the docgraph extension installed
(https://pypi.python.org/pypi/hg-docgraph).
Then run the test-topic-tutorial.t and test-tutorial.t to update the output if
needed.
You'll need the dot binary (likely installed by the graphviz package in your
package manager) in order to have graphviz graphs rendered in the html output.
Simply run make in the docs directory should takes care of the conversion of
the tutorial .t files into .rst files. Then sphinx should do the rest of the
jobs by rendering graphviz graphs.