Add a compile time check for all methods to be invokable

When exposing a manually written class using the autogenerated *SourceAPI template class a check for all methods of the rep file is done.

This check is not enough and needs to be extended to also make sure the methods are invokable using Q_SLOT oder Q_INVOKABLE. Otherwise the map contains a -1 as methodIndex.

Trying to call this results in wrong error message which is not very helpful:

Invalid method invoke packet received. Index = 32 which is out of bounds for type "<class>"