Merge pull request #327 from SrNetoChan/screenshots

Users Manual Screenshots
print composer, overviews of map item explained
updated screenshot label item print composer, removed 2 screenitems, updated text
Merge pull request #328 from diethard2/master

print composer, overviews of map item explained.
image composer item updated, screenshot + text
Merge pull request #329 from diethard2/master

image composer item updated, screenshot + text
added the data defined button to guideline and added option to use URL for composer images items
Merge pull request #330 from diethard2/master

added the data defined button to guideline and added option to use URL f...
5 screenshot composer legend
Merge pull request #331 from diethard2/master

5 screenshot composer legend
improving the composer legend item
Merge pull request #332 from diethard2/master

improving the composer legend item
finished update of legend composer item
Merge pull request #334 from diethard2/master

finished update of legend composer item
composer scalebare 3 screenshot + changes screenshot in print composer manual
Merge pull request #335 from diethard2/master

composer scalebare 3 screenshot + changes screenshot in print composer m...
finished update of scale bar composer item
Merge pull request #336 from diethard2/master

finished update of scale bar composer item
Set a few screenshots to 135 dpiresolution