blockdiag: new package

Blockdiag generates block-diagram image from spec-text file (similar to
Graphviz).

Also add its needed dependencies, funcparserlib and webcolors.
seqdiag: new package

Seqdiag generates sequence-diagram image from spec-text file (similar to
Graphviz).
actdiag: new package

Actdiag generates activity-diagram image from spec-text file (similar to
Graphviz).
nwdiag: new package

Nwdiag generates network-diagram image from spec-text file (similar to
Graphviz).
asciidoc: support extra filters (ditaa, mscgen, diag)

Also, slightly change the shebang fixup in the patchPhase so that it
handles optional [[:space:]] before the interpreter path (needed for the
filters).

To enable the extra filters, put this in packageOverrides:

  asciidoc = pkgs.asciidoc.override {
    enableDitaaFilter = true;
    enableMscgenFilter = true;
    enableDiagFilter = true;
  };
asciidoc: add support for qrcode filter
asciidoc: add support for matplotlib filter
aafigure: new package

aafigure is an ASCII art to image converter.

Manual and example document:
http://launchpad.net/aafigure/trunk/0.5/+download/aafigure.pdf
asciidoc: add support for aafigure filter
Merge pull request #999 from bjornfor/asciidoc-filters

Add support for additional Asciidoc filters