Improve log integration with AppVeyor

[csmager]

There were a couple of fairly inconsequential and primarily cosmetic issues that I'd noticed when AppVeyor runs a FAKE build script.

At the start, FAKE calls PrintDependencyGraph. This is written as multiple LogMessages, which the AppVeyor helper also writes to AppVeyor's message log in the Messages tab. There are two issues that arise from this:

1. Adding a message to AppVeyor seems to be processed asynchronously. As a result, there is no ordering guaranteed. Here's a snippet from a log for a failed build:

2. The call to appveyor AddMessage is included in a trace. This seems to be a little redundant:

3. The call to appveyor AddMessage fails when the message is empty:

4. The console output from FAKE is redirected by AppVeyor and logged. This loses all the colouring, so the log appears entirely in white. However, AppVeyor supports ANSI color codes.

The changes I've made address each of those points:

1. I've changed the dependency message to be written as a single multi-line message so this appears as a single message in the log on AppVeyor. This makes no difference when written to the console.

2. I've changed to disable tracing when sending a message to the AppVeyor message log.

3. I've changed to not send empty messages to the AppVeyor message log, avoiding the error that results.

4. I've added ANSI color code support and use this when we're running on AppVeyor. If other build servers have the same issue & support ANSI colors then perhaps this could be enabled for those too. I ran a quick test for all ConsoleColor values to show how these are rendered on AppVeyor:

[forki]

build is red. can you please check?

[csmager]

@forki just looking at it now. I had tested the build on one of my projects and it works as I'd expect.

The error is in one of the tests and relates to an invalid char - the char is part of the escape sequence for ANSI color codes. As they tests are running on AppVeyor, I guess buildServer will be set to AppVeyor. It'll probably have something to do with that.

[csmager]

@forki Issue seemed to be that because we were essentially bootstrapping FAKE in the test, it determined we were running AppVeyor. Because of that, the ANSI color codes were written to the trace (per my change). MSpec reports all the test results to HTML, and the escape sequence contains a character that's not valid in HTML.

I changed to essentially toggle that option off in the class that contained the failing spec in an Establish function. I've not used MSpec before, so there may be a more appropriate way of doing that.

[csmager]

Eurgh, my VS code settings have trimmed a load of whitespace in the files I've edited. If you want me to revert those, just shout.

[forki]

thanks!