added copyright statement
convert XML writer to use QXmlStreamWriter
improve saving speed by caching in XMLDB::FileWriter::writeCategoriesCompressed
Use a Hash instead of a map in XMLDB::FileWriter::shouldSaveCategory in this use case (with <10 keys) it is faster
only lookup useCompressedIndexXML once per save, and remove last traces of export-in-2.1-format
opimization: make regular expression static, as this code is called a lot, and it never changes
added copyright
cmake: invoke `git` in the correct source directory

Without this change, out-of-source-tree builds were not getting the git version
information.
cmake: show the actual version info in the build output

Given that the message is always unconditionally here, we might as well include
the determined version informaiton in there.
Initialize the action state to a proper value

Without this, you'd have to press Ctrl+I twice in order to get rid of an infobox
if you have it configured to show by default.