[rigo.models.application] add cached argument to avoid querying the WS
[rigo.ui.gtk3.models] add cached keyword argument to get_icon
[Rigo] use only cached UGC metadata if user is scrolling the TreeView

This improves the scrolling speed greatly and reduces the network
pressure.
Release Entropy 205
Tagging Entropy version 205
[entropy.db.sqlite] expose default cache size to _CACHE_SIZE
[entropy.db.sqlite] make _setCacheSize() and _setDefaultCacheSize() protected methods
Add a DTD for the Entropy Package metadata.
[entropy.misc] update package.dtd, make versiontag optional
Complete package.dtd, add source-mirrors and pkg-changelogs elements
Add a sample package metadata xml using package.dtd as schema
package.dtd: add enc attribute to <license>
Place <provided-mime> after <signatures> in package.dtd
Add EntropyRepository.getPackageXmlData() method to output xml package metadata
Fix element order in package.dtd, signatures must follow extra-downloads
Fix license element syntax in package.dtd
Merge remote-tracking branch 'upstream/master'