updated version string to 15.0-testing

git-svn-id: svn://svn.code.sf.net/p/nzbget/code/trunk@1157 b1b436ca-2b18-4f33-ab5d-510789358d54
fixed: quick par-check could hang on certain nzb-files containing multiple par-sets (occured only in 64 bit mode)

git-svn-id: svn://svn.code.sf.net/p/nzbget/code/trunk@1158 b1b436ca-2b18-4f33-ab5d-510789358d54
fixed: menubar icon was not visible on OSX in dark mode

git-svn-id: svn://svn.code.sf.net/p/nzbget/code/trunk@1159 b1b436ca-2b18-4f33-ab5d-510789358d54
system sleep on idle state is now prevented during download and post-processing (Mac OSX only)

git-svn-id: svn://svn.code.sf.net/p/nzbget/code/trunk@1160 b1b436ca-2b18-4f33-ab5d-510789358d54
Merge master