src: clazy compiler warnings

get rid of most clazy warnings (https://github.com/KDE/clazy)
* range loop use refs
* qcolor ctor with ints
* missing Q_OBJECT macro
* use .constfirst instead of .first

enabled ccache for unix systems for fasterr recompiling
* if ccache is in path we use it now

src/lib_java/data/indexer/IndexerCommandJava.cpp

@@ -29,7 +29,7 @@ size_t IndexerCommandJava::getByteSize() const
 {
 	size_t size = IndexerCommand::getByteSize();
 
-	for (auto i : m_classPath)
+	for (auto& i : m_classPath)
 	{
 		size += sizeof(std::string) + i.str().size();
 	}