important Heritrix-settings should be included in setting.xml

Currently many of the Heritrix-settings are hardwired or defined as constants
in HarvestControllerServer.java and other classes.
The following settings should be defined in settings.xml:
1) Max size of arc-files.
2) Heritrix-settings-directory (by default="settings")
3) Heritrix-arc-file-directory (by default="arcs")
4) Compress arc-files (true/false)
I suggest the following extension to settings.xml:
<dk>
<netarkivet>
<heritrix>
<max_arc_size>524288000</max_arc_size>
<settings_dir>settings</settings_dir>
<arc_directory>arcs</arc_directory>
<compression>false</compression>
</heritrix>
..
</netarkivet>
</dk>
NOTE: This bug is originally from Bugzilla bug_id=296.
This bug was previously assigned to Unassigned.