Dependency system for Hypernucleus

Hypernucleus should find <dependency> tags under each game and download and install the corresponding dependency. The dependency should be added to sys.path when game is ran.

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Example:
A game depends on twisted.
<game>
<dependency>
<modulename>twisted</modulename>
<version>2.5</version>
</dependency>
</game>

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It should then find the corresponding dependency...
<dependency>
<name>Twisted</name>
<version>2.5</version>
<modulename>twisted</modulename>
<archiveurl>http://mysite.com/deps/twistedlinux25.tar.bz2</archiveurl>
<operatingsystem>linux</operatingsystem>
<architecture>32</architecture>
</dependency>

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<operatingsystem>linux</operatingsystem>
<architecture>32</architecture>
are optional... if they are not specified, then it should ignore them.
These two arguments are specified in the configuration file and set
via options in the preferences dialog.

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It needs to match the versions between the two <dependency> tags too.
Archives are downloaded to the archives folder, extracted to the dependencys folder and then deleted.
A class exists in the source code to work out paths.