homogenize file naming in gentle gis introduction
created section style manager
extended the style manager section
Merge pull request #164 from alexbruy/docs-homogenize

homogenize file naming in gentle gis introduction
updated vector and raster menu, implemented a reference to openstreetmap
updated qgis legend and status bar
more explanation on system environment variables, plus screenshot
figure for system environment variables
further explanations System menu
little changes
read through the sections and commented out disclaimer if files are ready
added wcs support and some minor updates
update wcs info with help from Radim, update new icon
completed non spatial tables, read through the user manual and improved text
as pushed to tx as sources
all updated po file from tx (as backup)
final check for getting started
added missing icons, final check of qgis_gui section
checked until annotation tools
upgrading theme to site theme + pdf build of pyqgis cookbook