[Feat] JSON output to r.volume

[cwhite911]

The r.volume tool currently provides ouput as follows.

r.volume input=elevation clump=geology_30m

#
# Volume report on data from <elevation> using clumps on <geology_30m> raster map
#
# Category   Average   Data   # Cells        Centroid             Total
# Number     in clump  Total  in clump   Easting     Northing     Volume
# -----------------------------------------------------------------------------
#      217    118.93  86288828  725562   635325.00   221535.00    8628882798.63
#      262    108.97  21650560  198684   638935.00   222495.00    2165056037.02
#      270     92.23  63578874  689373   642405.00   221485.00    6357887443.53
#      405    132.96  33732662  253710   631835.00   224095.00    3373266208.59
#      583    139.35   3011288   21609   630205.00   224665.00     301128821.55
#      720    124.30    599618    4824   634075.00   227995.00      59961816.06
#      766    132.43    936791    7074   631425.00   227845.00      93679120.08
#      862    118.31   7302317   61722   630505.00   218885.00     730231746.74
#      910     94.20   4235816   44964   639215.00   216365.00     423581613.11
#      921    135.22   1693985   12528   630755.00   215445.00     169398523.05
#      945    127.24      1145       9   630015.00   215015.00        114512.03
#      946     89.91    365748    4068   639085.00   215255.00      36574833.85
#      948    129.02    112632     873   630185.00   215115.00      11263181.57
# -----------------------------------------------------------------------------
#                                                 Total Volume = 22351026655.81

We should add the ability to output in a JSON format.

r.volume input=elevation clump=geology_30m format="json"

[
  {
    "category":  "int",
    "average":  "number",
    "sum":  "number",
    "cells":  "int",
    "volume": "number"
    "easting": "number",
    "northing": "number"
  },
  {
     "..."
  }
]

Additionally:

• The current -f flag should be deprecated and instead we will have format=csv.
• Add separator parameter to be able to change the csv output
• Add -p flag for printing (to standard output or file). Now it will print even without the -p flag but in a future release user will need the flag.