Init with constant value for moving average, removal of JAVA and fixed point

There is a new optional parameter which allows init of the coefficients with a non-zero value. This is useful for moving average filters.
Support for JAVA has been dropped as it's not automatic and been drifting away from the C++ class.
Fixed point also hasn't been kept in sync with the floating point version and removed.

Minor fixes

This adds exceptions to the java wrapper and Nick has tidied up the swig wrapper.

Coefficient getters

Thanks to Nick Bailey we have now a getter to get the coefficients back to both C++ and Python. That's in particular useful for LMS filter applications.

More options for the constructor: coefficients as a C++ std::vector

Added an additional constructor where you can provide the coefficients as std::vector which is useful when creating coefficients iteratively and adding them one by one.

A few minor bug fixes and the JAVA wrapper has now the *aar files included here for direct use in an Android project.

Performance enhancements

All realtime filtering operations are now in the header file with the "inline" directive so that they can be directly compiled into the main program and optimised as needed.

Java wrapper bugfix release

The JAVA wrapper for LMS had the wrong type in the constructor which could have resulted in the wrong number of taps. Fixed now.

New constructor for const arrays

Added a constructor for const arrays which has the benefit of known length of the array so that segfaults can be prevented by design.

Fixed a bug in the Fixed point version which didn't copy the coefficients over.

Also added a lot of details to the documentation and made it doxygen friendly.

Multiplatform / Multi language release

C++: The coefficients are now copied over into its own memory within the class. The class then takes care of the memory management.

JAVA / Android: fully working FIR filter as an Android AAR.

Python: Tested under Linux, Windows (binary / from source) and under Mac (via homebrew installed python3/pip3).