Remove dot-underscore files. Merges ._* files with corresponding native files.

# To merge all '._*' files recursively:
dot_clean <path/to/directory>

# To don't recursively merge all '._*' in a directory (flat merge):
dot_clean -f <path/to/directory>

# To merge and delete all '._*' files:
dot_clean -m <path/to/directory>

# To only delete '._*' files if there's a matching native file:
dot_clean -n <path/to/directory>

# To follow symlinks:
dot_clean -s <path/to/directory>

# To print verbose output:
dot_clean -v <path/to/directory>