support multi definition of assemblies in assembly property

with this enhancement one can now have multi language without the need of using the bootstrapper or multi module. 

Fxcop runs once for all solution, for example if https://github.com/SonarCommunity/sonar-resharper/pull/1 is merged you can have:

sonar.visualstudio.enable=false
sonar.scm.enabled=true
sonar.scm.url=scm:git:http://stash/scm/ts/structures
sonar.cs.fxcop.fxCopCmdPath=c:/Tekla/BuildTools/FxCop/FxCopCmd.exe
sonar.resharper.inspectCodePath=c:/Tekla/BuildTools/resharpercli/inspectcode.exe
sonar.sourceEncoding=UTF-8
sonar.sources=.
sonar.visualstudio.outputPaths=../../BuildDrop/Work/bin
sonar.cs.opencover.reportsPaths=*.coverage.xml
sonar.stylecop.projectFilePath=./TeklaStructures.sln
sonar.resharper.solutionFile=TeklaStructures.sln
sonar.cs.fxcop.assembly=../../BuildDrop/Work/bin/Assembly.dll,../../BuildDrop/Work/bin/Assembly2.exe
sonar.cs.fxcop.directory=../../BuildDrop/Work/bin

And everything gets imported correctly into sonar without any additional configuration from the user side. This is much simpler than defining modules one by one.

Please consider this enhacement