Update install_fireworks.xml

use Modifications.***.php instead of ThemeStrings
Delete ThemeStrings.english-utf8.php
Delete ThemeStrings.english.php
Delete ThemeStrings.polish-utf8.php
Delete ThemeStrings.polish.php
Update package-info.xml
Update install_fireworks.xml

unix servers... :)
Merge pull request #1 from phantomm/1

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