Added various command-line options.
Created a foundation for adding more options.
Currently implemented: --port, --host and --onlinemode

Some server hosters, especially those who have payment options on a per-slot basis, customize runtime parameters to restrict server owners from exceeding their limits. Glowstone currently has limited support for command line options.

This commit adds a foundation for command-line options and implements --host, --port and --onlinemode

This commit also formats the help message that it shown when running GlowStone with the --help switch.
Fixed gradle manifest reference. Thanks @Grinch, @scooterboo, @lukespragg.
Changed wgen to treat 128 as world height in all cases (fixes #151).
Corrected when fallback commands are registered.
Added generateExtBlockSections support and handled generator errors better.
Revamped bulk sending to split chunks by how big they are.
Fixed InteractEntityMessage decoding (fixes #163).
Fixed decoding of client brand, some PluginMessage tidying (fixes #161).
Fixed sneaking and sprinting handling in PlayerActionHandler (fixes #165).
Tidied error messages on unclean disconnects (fixed #110).
Added block placement handling for several blocks (see #119).

Placement handling for dispensers, droppers, levers, furnaces, and
hoppers. Right-click (toggle) handling for levers.
Merge with GlowStone upstream