Move installation profile location and update instructions

[quicksketch]

As part of adopting Features, we need to move the installation profile to an expected location. Right now Mukurtu 4 isn't following the traditional naming conventions of Drupal because the mukurtu.info.yml that defines the install profile lives inside of a directory named mukurtu-cms. Typically project directory names match the .info.yml file name, and this mismatch trips up Features module.

It would be good to correct this location for Features, and to prevent unexpected problems with other code that may make the same assumption.

We discussed this week that while we're renaming the directory, we should also eliminate the contrib parent directory, which is superfluous for a distribution where there's only ever going to be one profile.

Current installation profile location:

web/profiles/contrib/mukurtu-cms/mukurtu.info.yml

Proposed installation profile location:

web/profiles/mukurtu/mukurtu.info.yml