Version 1.6.alpha
 - Use 'find_program' instead of 'dependency' for vapigen
 - Add functionallity for zoom-on-double-click
 - Implement global-state expressions for vector stylesheets
 - Add 'changed' signal for viewport (consolidating latitude, longitude, zoom level)
 - Fix some memory leaks
 - Remove option to build without the vector renderer

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Version 1.5.0.1
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 - Re-tagged due to broken 1.5.0 tag