Support explicit tsconfig.json parameter

[saschanaz]

tsc -config tsconfig-debug.json

This will help when user need several build settings without separate build system.

For example:

{
    "version": "0.1.0",
    "command": "tsc",
    "tasks": [
        {
            "taskName": "release",
            "args": ["-p", "."]
        },
        {
            "taskName": "tester",
            "args": ["-config", "tsconfig-debug.json"]
        }
    ]
}

[mhegazy]

looks like a dupe of #2869