[Feat] - Add JSON output to g.mapset

[cwhite911]

Add JSON output to g.mapset.

The addition should include outputs for the following commands.

1. Print the current mapset and exit.

g.mapset -p format=json

{
    "project": "nc_spm_08_grass7",
    "mapset": "user1"
}

2. List available mapsets and exit.

g.mapset -l format=json

{
    "project": "nc_spm_08_grass7",
    "mapsets": ["landsat" ,"new" ,"PERMANENT", "user1"]
}

3. Create mapset if it doesn't exist

g.mapset -c mapset=user2 project=nc_spm_08_grass7 format=json

Output the new mapset.

{
    "project": "nc_spm_08_grass7",
    "mapset": "user2"
}

4. Change current mapset

g.mapset mapset=user2 project=nc_spm_08_grass7

Output the current mapset.

{
    "project": "nc_spm_08_grass7",
    "mapset": "user2"
}

[cwhite911]

This is a template for future JSON related issues.

[petrasovaa]

Not sure about points 3 and 4, I would say no output needed.

[wenzeslaus]

The classic Unix tool approach to say nothing if the request operation was done.

[cwhite911]

I was thinking about it more like a REST API.

[wenzeslaus]

Do you have an example? For unix tools, there is plenty, rm is one, but interestingly Git is a counter example.

Ultimately, we want the tools to be useful, convenient, and predictable.