Differences from XTide 1

[As if anybody remembers XTide 1. This section is now obsolete.]

XTide 2 is a complete redesign of XTide 1. There are too many subtle improvements to list them all, but here are the not so subtle ones:

New interactive user interface for X windows client
Integrated web server now provided in distribution
Simpler, better command line interface
Handles multiple harmonics files transparently
Subordinate stations are now stored in an external database and are expanded to handle all known styles of offsets
Hydraulic currents are fixed
Removed useless options and modes
Added sun and moon information (by popular demand...)
Fast, efficient binary format for harmonics data

These are the non-obvious things you must know in order to migrate:

The environment variable HFILE is no longer used to specify the harmonics file; instead, HFILE_PATH is used:
```
export HFILE_PATH=/usr/local/share/xtide/harmonics.tcd
```
If HFILE_PATH is not set, XTide looks for the file "harmonics.tcd" in the default directory.
XTide now has its own built-in icon. Remove any icon settings that you made in your window manager init files. [Since the icon protocol that XTide 2 uses is no longer supported by newer window managers, that advice can be disregarded.]
You may no longer use anonymous units in harmonics files. The units must be one of the recognized alternatives. These are: feet, meters, knots, knots^2 (for hydraulic currents). If you are still using an ancient harmonics file that contains no units or "bogo-knots," then shame on you. It's high time that you upgraded.