[build] Remove PyYAML dependency

This converts all the YAML files to JSON files, as json parsing is built
into python instead of being a separate library requiring installation.

YAML is a superset of JSON, but putting comments in is not quite as obvious
as it is in yaml.

The following glue was used to convert yaml to json:
python -c 'import sys, yaml, json; json.dump(yaml.load(sys.stdin), sys.stdout, indent=4)' < $1 > $2

Clearly I haven't tested this on every single platform, and this
doesn't address the large blobs of yaml in the lpc4300 scripts directory,
only the cortex NVIC generation process.

I've tested a few IRQ driven example apps, and I've checked the generated
output of some known cases like the LM3s that has explicit gaps, and they are
all generated correctly.

README

@@ -35,19 +35,14 @@ TIP: Include this repository as a GIT submodule in your project. To make sure
 Prerequisites
 -------------
 
-Building requires python, and a python YAML module. (Some code is generated)
+Building requires python. (Some code is generated)
 
-For Ubuntu
- $ [sudo] apt-get install python-yaml
-
-For Fedora
- $ [sudo] yum install PyYAML
+For Ubuntu/Fedora, you already have everything you need.
 
 For Windows
  Download and install:
  msys - sourceforge.net/projects/mingw/files/MSYS/Base/msys-core/msys-1.0.11/MSYS-1.0.11.exe
  Python - http://www.python.org/ftp/python/2.7/python-2.7.msi (use installer to get the right registry keys for PyYAML)
- PyYAML - http://pyyaml.org/download/pyyaml/PyYAML-3.10.win32-py2.7.exe
  arm-none-eabi toolchain - for example this one https://launchpad.net/gcc-arm-embedded
  Run msys shell and set the path without standard Windows paths, so Windows programs such as 'find' won't interfere:
  export PATH="/c//Python27:/c/ARMToolchain/bin:/usr/local/bin:/usr/bin:/bin"