[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.

include/libopencm3/lpc13xx/irq.json

@@ -0,0 +1,63 @@
+{
+    "irqs": {
+        "0": "pio0_0", 
+        "1": "pio0_1", 
+        "2": "pio0_2", 
+        "3": "pio0_3", 
+        "4": "pio0_4", 
+        "5": "pio0_5", 
+        "6": "pio0_6", 
+        "7": "pio0_7", 
+        "8": "pio0_8", 
+        "9": "pio0_9", 
+        "10": "pio0_10", 
+        "11": "pio0_11", 
+        "12": "pio1_0", 
+        "13": "pio1_1", 
+        "14": "pio1_2", 
+        "15": "pio1_3", 
+        "16": "pio1_4", 
+        "17": "pio1_5", 
+        "18": "pio1_6", 
+        "19": "pio1_7", 
+        "20": "pio1_8", 
+        "21": "pio1_9", 
+        "22": "pio1_10", 
+        "23": "pio1_11", 
+        "24": "pio2_0", 
+        "25": "pio2_1", 
+        "26": "pio2_2", 
+        "27": "pio2_3", 
+        "28": "pio2_4", 
+        "29": "pio2_5", 
+        "30": "pio2_6", 
+        "31": "pio2_7", 
+        "32": "pio2_8", 
+        "33": "pio2_9", 
+        "34": "pio2_10", 
+        "35": "pio2_11", 
+        "36": "pio3_0", 
+        "37": "pio3_1", 
+        "38": "pio3_2", 
+        "39": "pio3_3", 
+        "40": "i2c0", 
+        "41": "ct16b0", 
+        "42": "ct16b1", 
+        "43": "ct32b0", 
+        "44": "ct32b1", 
+        "45": "ssp0", 
+        "46": "uart", 
+        "47": "usb", 
+        "48": "usb_fiq", 
+        "49": "adc", 
+        "50": "wdt", 
+        "51": "bod", 
+        "53": "pio3", 
+        "54": "pio2", 
+        "55": "pio1", 
+        "56": "ssp1"
+    }, 
+    "partname_humanreadable": "LPC 13xx series", 
+    "partname_doxygen": "LPC13xx", 
+    "includeguard": "LIBOPENCM3_LPC13xx_NVIC_H"
+}

include/libopencm3/lpc13xx/irq.yaml

@@ -1,62 +0,0 @@
-includeguard: LIBOPENCM3_LPC13xx_NVIC_H
-partname_humanreadable: LPC 13xx series
-partname_doxygen: LPC13xx
-irqs:
-  0: pio0_0
-  1: pio0_1
-  2: pio0_2
-  3: pio0_3
-  4: pio0_4
-  5: pio0_5
-  6: pio0_6
-  7: pio0_7
-  8: pio0_8
-  9: pio0_9
-  10: pio0_10
-  11: pio0_11
-  12: pio1_0
-  13: pio1_1
-  14: pio1_2
-  15: pio1_3
-  16: pio1_4
-  17: pio1_5
-  18: pio1_6
-  19: pio1_7
-  20: pio1_8
-  21: pio1_9
-  22: pio1_10
-  23: pio1_11
-  24: pio2_0
-  25: pio2_1
-  26: pio2_2
-  27: pio2_3
-  28: pio2_4
-  29: pio2_5
-  30: pio2_6
-  31: pio2_7
-  32: pio2_8
-  33: pio2_9
-  34: pio2_10
-  35: pio2_11
-  36: pio3_0
-  37: pio3_1
-  38: pio3_2
-  39: pio3_3
-  40: i2c0
-  41: ct16b0
-  42: ct16b1
-  43: ct32b0
-  44: ct32b1
-  45: ssp0
-  46: uart
-  47: usb
-  48: usb_fiq
-  49: adc
-  50: wdt
-  51: bod
-# 52: reserved
-  53: pio3
-  54: pio2
-  55: pio1
-  56: pio0
-  56: ssp1