Migration messaging improvements

[ErisDS]

This builds on #6621 and ended up being a little more involved than I had originally intended. To start with I just added a flag to logInfo so that it would output the message differently - but the code was instantly harder to read and the tests became very hard to reason about.

Plus, I know, really, we need to move towards having proper 'loggers' as per #2001 and this uses the right sort of pattern.

So.. instead of passing a single logInfo method around the migration system, we now pass around a logger object which has an info and a warn method. They do similar things - prefixing a message with either 'Migrations:' or 'Skipping Migrations:' and adding a colour. The normal message is blue, the warning is yellow.

Everywhere in the data & fixture migrations where a migration is skipped over, a warning message is now being output.

So, if I run a simple 003->004 migration, I get output like this, where you can see I didn't have any badly formed tags:

And then if I use FORCE_MIGRATION=true npm start to get the migrations to run a second time, I get this:

And we can easily see that none of the migrations actually ran.

The aim here is just to make debugging easier & make things a little more explicit and clear. Hopefully we'll reap the benefits later 😁

refs #6301

• fix messages that joined with comma and therefore missed outputting version no
• change logInfo to logger that has both an info and a warn method
• add new warn method to errors
• add a warn message every time a migration (data or fixture) gets skipped over
• update logger everywhere, including tests
• update tests to check logger.warn gets called