Support installing plugins from a local directory

It would be convenient if micro -plugin install would accept a path to a directory as an argument. This would be a bit more convenient for development. It's better than editing my source code in my home directory or constantly copyin g things. The alternatve that I currently use though is I use the environment variable to tell micro its configuration is located in my development tree: MICRO_CONFIG_HOME=$(pwd)/micro $(pwd)/result/bin/micro , however I still have to either put the code in the config dir, or symlink individual files because of the symlink bug.

There are also two possible scenarios

• the target is copied into micro's directory as with normal plugins: this means editing the original directory will not influence what's running
• it's symlinked: opposite of the above

It's not obvious to me that either of these would necessarily be superior so both could be done.

Symlink support would need to be fixed for the latter: https://github.com/zyedidia/micro/issues/1949

Start at the micro -plugin install command path and read issue #1949 for the symlink limitation. Decide whether a local directory should be copied, symlinked, or support both, then verify the chosen behavior for a directory argument and development edits.