Update „LaTeX Watch”

Hi,

this pull request contains updates for the “LaTeX Watch” command. It adds the following features:

- The command now uses `latexmk` instead of `etex` and `pdfetex`. The whole document will be translated without the need to use external tools like `bibtex` or `makeindex`. Sadly this means that the whole updated cycle will be — at least on the first run — a bit slower.

- The script now supports `%!TEX TS-program`. You can specify the engine you want to use for watching your file directly inside the tex file.

- The command supports `xelatex` and `lualatex`. To use `lualatex` you need to specify it as typesetting program directly inside the tex-file. Add the following directive at the start of the file: `%!TEX TS-program = lualatex`.

- Fix support for “TeXShop”: Previously watching a documents using “TeXShop” would fail.

It also introduces the following changes:

- The files created during the translation process will *not* be prefixed with a dot. This means that you will see them inside Finder. To remove the auxiliary files after you are done, just close the window of the PDF viewer. If you want to keep the files hit `^⌘W` and click `Ok` to stop watching the tex file. 

- In case of error the script now shows the log output of `latexmk` instead of the log file from `etex` or `pdfetex`. This log is sadly even longer than the one generated by  `etex/pdfetex`. However, you should find the errors in the tex file easily by looking at the error summary provided at the end of the log file.

- The script now uses a maximum line width of 80 characters.

The changes introduced in the commit should (hopefully) fix the following issues:

- #58: Watch document doesn't include makeindex

- #66: Watch Document Doesn't work

Thanks a lot to Robin Houston for providing such a nice way to work with TeX documents. I hope I did not introduce too much errors to your excellent script.