cleanup & optimization

- In Dockerfile switched from ADD to COPY for files.
- Configuration moved from using RUN & sed lines, to "COPY sshd_config".
- Dockerfile made more readable
- One less layer used by Dockerfile, e.i layer optimization.
- Removed pwgen as a dependency and replaced with /dev/urandom, pipes, etc...
- Added .dockerfile
- Added sshd_config
- Improved helper script error messages.
minor adjustments & file additions

- Example fig files (used for testing) added for benefit of all.
- Minor clarifications in logging messages for runtime script.
bugfix for issue #1

- Fixed issue with using existing users, (not added to sftpusers)
replaced user setup

- Added a new setup system featuring:
  - Suport for multiple users in single docker run
  - Map any uid or gid to a sftp username of your choice
  - Easy syntax, using the familiar old env vars
- Minimized log spam, showing messages only when necessary
- Removed sftpusers in favor of forcing sftp on all
- Switched from shared home, to user specific,
  (more volumes in exchange for flexibility)
Merge branch 'beta'

Conflicts:
	entrypoint.sh