This enables access to the subcommands from the main command. It keeps the commands not documeneted at the top level, so they remain hidden and experimental.

The lock and unlock, now under 'grass mapset lock' and 'grass mapset unlock', are accessible from outside of GRASS through CLI (no Python API or GRASS tools), providing a way of other applications (such as QGIS) to use GRASS locking when accessing GRASS mapsets.

Given that lock and unlock are under mapset (they are too low level to be at subcommand top level), it is clear there should be also project. The create_project function is readily available for CLI use (espetially after OSGeo#6415), so it is now under 'grass project create' and the subcommand is utilized in tests.

For symmetry, this adds also 'grass mapset create' which uses the semi-internal function grass.grassdb.create.create_mapset. The function parameters were adjusted to allow for a single path being provided (which was already supported through path resolution function).

The create_project function was also improved by adding description parameter as full word replacing (but keeping) desc parameter. The behavior was sligtly changes so that MYNAME is only created when description is provided which is what the documenetation suggests ('desc...creates MYNAME file'), but it was implemented that MYNAME was always created even if empty. Finally, missing documentation for the CRS parameter was added.

The new structure in the cli file is that project and mapset subcommand parser definitions have their own functions. This minimizes name conflicts and keeps the main function short.

Finally, 'grass run' subcommad now has --project to use an existing project (defaulting to PERMANENT mapset) or a mapset within that project. This is needed now for testing the created project using the subcommand interface.