fixes #13

fixes #18

This allows int-vectors to be multiplied by float-scalars, producing
accurate int values (e.g. 4.2 * 10 == 42).

Re-added back all tests, including CPU and GPU. Re-added multi row lengths. Commiting for backup purposes.

Added elements into set compressed row lengths to test getNonZeroElements correctly. Set the row length to the same value, for easier testing. Commiting for backup purposes.

Moved test implementations to _impl.h. Reformatted code. Changed long commented out sections to fake ifdef.

Added ChunkedEllpack to testing. setCompressedRowLengths test is broken, commiting for backup purposes.

Fixed and reformatted setCompressedRowLengths test function. Found error for setRow test function, it is possibly in the implementation of SlicedEllpack.

Added Ellpack and SlicedEllpack to tests. Changed setCompressedRowLengths test to make it work with all Ellpacks. setRow test is broken for SlicedEllpack. Commiting for backup purposes.

Added Type instead of all int indexes. Formatted includes to top of file. Removed the need for using namespaces.

Added Type instead of all int indexes. Formatted includes to top of file. Removed the need for using namespaces.

Added template testing for all working tests. Implemented RealTypes and occasionally IndexType instead of int/float/etc. Updated TODO.