Warnings/errors are not reported nicely

[akerbos]

It may be useful to provide some digest of the generated log(s). For example, counting warnings and warnings in the output of pdflatex can give simple feedback towards how good or bad the run was.

[akerbos]

The above applies to both engines and extensions: no warning/error should be lost! CLI should indicate that there were problems, and the log should contain (pointers to) the detailed messages.

[akerbos]

Ultrafeature: if/when we can reliably collect warnings and errors, create a structured log (Markdown?) which can (optionally) directly be converted into PDF or HTML.

That probably means that engines and extensions have to do the heavy lifting and return four values:

• log -- the raw output string
• errors -- an array with all errors
• warnings -- an array with all warnings
• hints -- an array with miscellaneous messages

[akerbos]

Tentative to-do: add a machine-readable text format.

[akerbos]

This is what PDF logs look like now:

[akerbos]

Aside from the TikZ extension which will be dealt with during the cleanup (cf issue #24), everything is done.

[akerbos]

As of 248aa38, tikext does collect, parse and propagate messages correctly.