More consistent file operation messages

[achilleas-k]

All file operations are announced before they are executed. These operations are add, commit, get-content, remove-content, lock, unlock, and upload. If no file is affected by the operation, the message "Nothing to do" is printed. In direct mode, the lock and unlock commands inform the user that files are always in an unlocked state.

None of these changes affect the JSON output. No-ops still do not print anything when JSON output is requested.

Additional changes:

• The lock and unlock commands now require at least one path argument. Previously, a blank argument list (i.e., gin unlock and gin lock) would behave identically to gin unlock . and gin lock . (where . = all files under current working directory). gin unlock and gin lock with no arguments are now errors and will print the command usage.
• Download no longer locks all files. The download command would previous lock every unlocked file in the repository. This is no longer the case. If a file has been replaced or updated on the server and it is currently unlocked, the behaviour is the same as a pull merge conflict. In other words, the user will be informed that a local file will be overwritten by the download.

Closes #246

[achilleas-k]

Disabled (commented out) new --verbose flags. The new feature needs a tiny bit of work still and I'd like to release the fixes in this and the previous PR as soon as this is merged.